Guide to Getting It On is definitely worth some attention. It's very thorough as well as entertaining. link

I have none right now but I do enjoy a book I review about sexual massage, its very spiritual and I'm really into that stuff. One day I will probably get the pink book on squirting that is getting many good review. Don't really know the title by heart though.

All my educational type books are BDSM related which I certainly couldn't recommend to everyone.. I don't even know. Maybe the Kama Sutra or a version of it?

I recommend "Sex for One" by Betty Dodson to my friends who have never masturbated or are timid about it.
For BDSM books, I recommend "Screw the Roses" for intro, and "The New Topping", and "New Bottoming Book".
Local libraries sometimes have these books if you're near a metro area.

Even though these books have already been mentioned, I would like to throw in another nomination for The Guide to Getting It On, Opening Up by Tristan Taormino, and The New Topping/Bottoming Books by Janet Hardy and Dossie Easton. Though these are all totally different books, they have all been invaluable to me. The Guide to Getting It On is a no-nonsense, fun approach to sexual instruction, while Opening Up offers tons of practical advice for those interested in (or already in!) nonmonogamous relationships of all types. The Topping/Bottoming Books were the first ones I read when I was discovering my interest in BDSM, and they served me well. I think they are a must-read for anyone interested in an introduction to kink.

Screw The Roses, Send Me The Thorns is a classic 'BDSM for beginners' resource. I personally loved it mostly because it focused on chemistry & attentiveness being the main ingredient for bdsm & role play scenarios, which definitely lends itself to all aspects of any romantic relationship.

Fetish Sex by Violet Blue is also pretty resourceful for beginner-to-intermedia te players.

For anal activities:

Jack Morin's Anal Pleasure and Health and Tristan Taormino's Ultimate Guide to Anal Sex for Women (not just for women!) would be the two I'd pick for the anal section.

I know there are some anal books that I haven't read, so this is by no means exhaustive.

For those interested in polyamory, swinging, or any other form of multiple partner play, The Ethical Slut is your bible.

The Good Vibrations Guide to Sex would definitely get my vote as a good choice for a general sex book, likely edging out The Joy of Sex for that same spot. It's more up to date, open-minded, and broader in scope than the parts I've seen of Joy of Sex (of which I admittedly don't own a copy but have perused a few times).

Exhibitionism for the Shy by Carol Queen
Multi-Oragasmic Woman by Mantak Chia
Spectacular Sex by Annie Sprinkle
The Whole Lesbian Sex Book
The Soul of Sex by Thomas Moore

Opening Up- Tristan Taormino
Urban Tantra- Barbara Carrellas
I Love female Orgasm- Dorian Solot

For women, I think Sex for One: The Joy of Selfloving by Betty Dodson is a real asset. If a woman can become comfortable with her own body and conscious of what she likes and doesn't like, she'll have a much better chance of being able to convey her preferences to her partner(s) in a gentle, matter-of-fact, uncritical manner.