Do you read physical or e-books? Used? What’s your go-to provider? BookWalker? Honto? AmazonJP? Syosetu?
Any tips or tricks? Sales?
I think it might be nice to perhaps get a wiki going describing each provider and any helpful hints which I can link from the website, but let’s get down some thoughts and collate the wiki later 
I buy ebooks from bookwalker. Importing physical books is expensive and takes a lot of time.
Although I sometimes buy whole series second hand from mandarake or single volumes from verasia, an EU shop for Japanese learners. They’ll import most books for you if you request it. Otherwise they have textbooks and a few manga series and other fiction books.
Mostly, I purchase physical books from CDJapan. Their selection is good and they offer coupons about once a month or so. The prices are low, but the shipping is exorbitant, so it’s best to purchase a large (20+) number of books all at once. If I only need to buy a couple books and can’t wait for my next big order, I use Kinokuniya; however, the cost per book ends up being higher even with the free shipping.
If I have to buy an ebook I use Bookwalker. Their ebook reader is not great and since the DRM hasn’t been cracked you have no option but to use it, and you cannot use Yomichan with it. However, the big point in their favor is that you don’t need to go through any hassle whatsoever with VPNs, Japanese addresses, or Japanese credit cards, and their app is not region locked. They also offer plenty of free books (both free to keep and free for a limited time), and have sales and coin back events on a regular basis.
For context, I live in the USA.
I can recommend Kobo Japan for eBooks. They have Adobe DRM which is fairly easy to remove with Calibre so you can read it on any device (iPad, eReader, Browser with Plugins, etc.)
The main difference to Bookwalker, Amazon, etc. is that you get the file and you are not bound to the Kobo ecosystem.
I use my foreign credit card without any issues. I also don’t need to use VPN.
I nowadays mostly buy my books through Amazon Kindle, and if I really really like the book I’ll pick up a physical copy through one of these sites:
(New)
(Secondhand, all require a proxy to ship)
I’ll definitely have to keep my eye on this. Removing DRM is a big plus for me, and while I’m still able to do it with Kindle stuff, you never know when that’ll change in the future.
I use Booklive for ebooks. It’s a sister company of Bookwalker. They offer basically the same service, but there are some slight difference (notability, you get a random discount every day, which favors visiting often). Sadly, it also means you are stuck with using their app to read books 
For physical books, I rely on my local library as much as possible (the major plus of living in Japan). When I have to, I usually buy second hand from Boofoff or
メルカリ (already mentioned in the thread).
Sometimes, I also randomly wander into a bookstore and just get whatever looks interesting (but that tends to be expensive, so I limit those visits)
(I live in the US.)
Physical:
Digital:
**I don’t have to use VPNs for any of those. I know that a lot of people think that you can only use Japan-issued credit cards, but my credit card works just fine on cmoa.jp. (Granted, I have a major-issued credit card.) Cmoa does allow you to use paypal and other options of payment, as well.
I pretty much only use Bookwalker and Kinokuniya for when I buy books. Occasionally I will use dlsite or dmm but that is mainly for visual novels rather than manga or books.
This is what I use as well. I don’t mind using a VPN, but I don’t want to deal with DRM or specific apps. Being able to strip the DRM means I don’t have to worry about losing access, I can covert manga to cbz and read them in my preferred reader, and I can do whatever I want with novel files (like run them through text analysis for fun).
The main downside is that the search is pretty terrible for anything that isn’t part of a title.
I buy physical and e-books in AmazonJP.
The physical ones come usually nicely packaged and they do customs paperwork for me for a reasonable shipping price and speed.
The e-books you can do magic redacted stuff, unlike some other places like Bookwalker, so you can side load on non-kindle devices. Gives you a bigger sense of ownership and freedom.
I used to buy on Honto and CDJapan for physical, but not anymore since the new IOSS legislation in EU, as that made everything extremely expensive if the paperwork is not done at origin.
I use the exact same places you do. I’ve lately been craving getting physical books so I’ve recently started getting manga from CDJapan and Kinokuniya.
Bookwalker supposedly you are able to read books offline, but I have tested this with airplane mode and the app just crashes/stops working on airplane mode. I too also love that it’s not region locked and you can switch to English when ordering a book so it’s super easy to use. When reading and if I want to zoom in to read the furigana above the kanji it gets kind of blurry sadly.
I buy Bookwalker primarily now, but have bought Honto and eBookJapan in the past. I’m intrigued by Kobo, I tried them a long time ago (2 years?) and found the store lacking, so perhaps it’s gotten better since then 
I do vastly prefer DRM free since Bookwalker has the incredibly stupid policy of limiting how many highlights you can do. I like to highlight names to make notes of readings, highlight interesting words, and highlight passages I struggle with to go back to review and that’s just not possible with the limits they have!
I also use Google Play books which also uses Adobe. They also allow in-browser reading that doesn’t block Yomichan which is quite helpful. Sadly their selection of Japanese books is incredibly limited and painful to browse. I halfway suspect they don’t even want to sell books!
I also read a ton of Aozora Bunko books/short stories which of course are out of copyright and freely available online. Not for everyone as old Japanese is a skill to learn in and of itself.
And I also get some physical books both due to living in an area with a large Japanese population so I have access to used book sales / unwanted books being given away free from the library / used book stores. I feel spoiled 
As much as I like physical books, they take up a lot of space, and are a hassle to drag around, so I generally only buy digital nowadays, which would be on Amazon JP.
I need to get on this. I’ve been thinking of ways to read physical books for cheap lately – specifically manga, since I’ve heard they’re not great on Kindle – and it wasn’t until last night that I remembered that libraries are a thing.
I’d like to point out that manga tend to have crazy wait time since they are very popular. I’ve made a reservation for 7seeds (vol 1-10) a few months ago, and the estimation was ~1.5 years wait time. I’m just too stubborn to give up.
Physical Books are my Jam! If your in the US, then…
eBay is where you get the steals, I got all of the Japanese version of How To Train Your Dragon that way. it was like $70 including shipping for like 11 books.
Though, in general, if you want a collection, Zenmarket is the way to go. Its +3 per item ordered, so if you get a set with like a book SET, it only 3$ +shipping (which is about $30+). So, you could get all of Percy Jackson and the Olympians for like $70. Its also good for older books, cuz that way you can find steals in the yahoo auctions area. For example I saw someone selling Tamora Cierce Trickster’s Choice/Queen series for like $40, which is a deal cuz no ones selling Book 2 for a reasonable price, and if you bought every book separately for a reasonable price, it would be like $44
If you want random books, (if they are newish cuz Kinokuniya doesn’t carry old books), Kinokuniya is your best bet, if you order enough stuff the shipping is free.
Amazon.com or ThriftBooks s probably the best if you’re only buying 1 book and you can’t find it on Ebay and its not in stock for Kinokuniya or you want a used version. Thriftbooks would have better prices than Amazon.com, but IDK when shipping gets involved. The Durarara Manga would be an example of this. Kinokuniya, amazon, thriftbooks
The only con to thriftbooks is that it often takes a long time for the book to pop up in a Japanese translation. Or at least, that’s been the case for everything on my wishlist.
I buy a mix of physical and digital.
For digital I use Amazon Japan. They have a vast library and it’s really easy to use. I remember having to use a VPN literally one time several years ago, and I had to put in a random Japanese address, but once you set it up once there’s no hassle. Also, it’s easy to remove the DRM using Calibre if you want to feel like you actually own what you bought. I exclusively buy novels / light novels this way so that I have easy dictionary access via my Kindle Paperwhite, but I also convert them to HTML format so I can more easily make flashcards in Kitsun. I also buy some digital manga, particularly when there are good sales.
I do still buy some physical manga a few times a year, for which I use CDJapan. I used to use Amazon Japan for that, but I had multiple bad experiences with them not securing the books at all (literally just thrown into the box), resulting in bent corners and torn obi. What finally pushed me to make the switch to CDJapan was when I wanted to buy ご注文はうさぎですか Complete Blend. One of the main things I insist on buying physically as much as possible is Manga Time Kirara series, because they use really high quality / thick A5 paper, which is better quality and bigger than typical manga (in my experience at least). ご注文はうさぎですか Complete Blend, essentially being a masterpiece edition of my favorite manga series, instead uses B5 paper (original size from the magazine) with dozens of color pages, and let’s just say I was NOT willing to put that to chance with Amazon Japan. CDJapan packaged that (and everything else) perfectly and I had a good experience with subsequent shipments as well, so I’m never going back to Amazon Japan for physical books.
First time I heard of CDJapan but I looked on their site and they had a ton of stuff that I’ve been wanting and seems a lot easier to order stuff there compared to Amazon. Thanks for mentioning them, I just placed an order now 
Physical: don’t have many, but I got two from Amazon US and two from Kinokuniya (as in the physical location, not online, so idk about shipping). I unfortunately don’t live near a place that sells Japanese books so I usually buy digital. I want to buy more physical books though so this thread is a great reference!!
Digital: I use Bookwalker! I like it for the most part, but I’ve noticed furigana tends to be blurry. btw, if you also buy books on Bookwalker, I highly recommend checking out The BookWalker Freebies Thread on the Wanikani forums. I’ve picked up a lot of free books that way
Also, if you are using Booklive, books that are free (or discounted) on Bookwalker will also be free (or discounted) there.
