Here is the list of reviewed books (+ their location; eg post 1 is this post)
How to Draw Manga: Getting Started post 4
How to Draw Manga: Vol 5 - Developing Shoujo Manga Techniques post 3
More How to Draw Manga: Vol 2 - Penning Characters post 5
More How to Draw Manga: vol 4 - Mastering Bishoujo Characters post 1
Manga Mania Shoujo: : How to Draw the Charming and Romantic Characters of Japanese Comics by Christopher Hart Post 2
I'll start off with More How to Draw vol 4: Mastering Bishoujo Characters
Firstly... I just want to say that the cover is NOT A GOOD REPRESENTATION of the book as a whole. The cover has some... scantily clad ladies on it, but the book is nowhere near as promiscuous as it looks.
This book covers the 12 stereotypical bishoujos...:
The strong girl
vulnerable girl
straight-laced girl
cutie
imp
shy girl
compassionate girl
bully
older girl
kid
princess
bad girl
Ok. Nudity: It shows most of the 12 girls in an example of lingerie (The imp has no clothes on, but everything is covered up by her legs and arms [she is sitting down]). There are a few panty shots (in the section of uniforms), but nothing too bad.
Barbie doll nudity is rampant, and is most often used to show the differences in the body types between the 12 girls. The most detailed it gets is dots for nipples. Almost 95% of the nudity is not used in a sexual manner, and the remaining 5% is to provide examples of 'sexy' characters. I was able to read through it and not be embarrased, but then again others might find this a stumbling block.
How it helped me: I'd say this is one of the best drawing books I have used; it shows alot of the stereotypes, including how to position the eyes, nose, mouth, posture, hair, height, hands, feet, etc to portray a character type you want. There is a vast array of costumes, and also gives some examples of model types to copy for the 12 girls (eg the bad girl - use rock or punk fashions for reference).
Overall: I would give it an 8. It lost 2 because of the lingerie shots (I found them unnecessary, but I suppose it is part of the bishoujo part of manga) and the cover. Stupid cover... it made my parents give me rather strange looks T__T
I should hopefully have a review of How to Draw Manga Vol 5: Developing Shoujo Manga Techniques up soon (bought it on ebay ^^ Yay! my first ever drawing book of my very own)