I have such a collection of physical books, including a bajillion of the SS エスエス magazines and New Pose Catalogue books, I wish I knew how to scan them without ruining the spines...
I also have that Nekomimi book mentioned somewhere above, and the Face Body Men's Moe Kakikata book someone wanted as well.
Not mentioned here (as far as I know), I have books on hands and feet (complete with a CD-rom with stock sketches), wrinkles in clothing, dynamic posing, perspective, photo catalog, etc. books. I'm trying to save up for more, but my recent financial situation and my bad habit of buying expensive figures is making it impossible to venture for more.

For myself, I'm hoping someone has or can scan:

https://otakumode.com/shop/57c528409dee4f071290ebbd/How-to-Draw-Common-Scenery

https://otakumode.com/shop/56727d8104d2efff010f2a2a/Cover-Designs-for-Doujinshi-Manga-that-Pop

https://otakumode.com/shop/5851f5e11c0e0b6602d31535/Visual-Background-Data-1-Girls-High-School-Coed-High-School-Elementary-Middle-School

https://otakumode.com/shop/56b1a6074944eac007ed0f17/How-to-Draw-Male-Muscles

https://otakumode.com/shop/57b4440ebd1855917359c827/Drawing-with-Digital-Tools!-How-to-Draw-Hair-that-Complements-Characters

https://otakumode.com/shop/56a046de9f6277d560b01bf5/Basic-Techniques-of-Character-Illustration-Taught-by-Animators

https://otakumode.com/shop/56727d9304d2efff010f2baf/Textbook-of-Line-Art-Design-as-Taught-by-an-Animator

https://otakumode.com/shop/56d3fa74af6ff1dc3ed37102/Textbook-of-Line-Art-Design-as-Taught-by-an-Animator-Vol-2

https://otakumode.com/shop/57143b99ba8be6207cd01eab/Real-Action-Pose-Collection-Vol-1-High-School-Girl-Action-Edition

And for my inner eroticist, while I don't NEED them, I'm really itching to witness exactly what kind of advice these books offer:

https://otakumode.com/shop/56ab161adf8c8603338cf373/How-to-Draw-Panties

https://otakumode.com/shop/56dfba2957143c8f5cd6a38e/How-to-Draw-Breasts