The most requested thing according to statcounter, as well as in emails, is asking for Ranma Hentai, more specifically the books at Ranmabooks. Surprisingly I recently received an email not asking as where to find them online for free, most can be found provided your google-fu is up to it, but asking as to whether I have read any of them and if I had are they worth the price.
In answer to that; I have read most, but not all, of them and am not currently a defender of the site (may or may not become one at some point in the future). I purchased legitimately through the site a few of the books the rest of the books I looked at were downloaded elsewhere. I'm not a large fan of Hentai to begin with since I prefer plots to mindless porn. The ones I purchased where done so while on sale, I personally think that they are a bit too expensive, but I am a cheapskate and when I do spend money I generally prefer to do so on things that are more substantial. In some ways I do not think they cost that much, since time and effort goes into making them and I have purchased a commission from an artist for pictures in the past that cost as much or more (depending on the book) per picture. If you do decide they are too expensive you could download them from one of the several places online that has them for free and if you do like it you could give a donation to the site.
Here are some small reviews of the books:
I dislike The Miss Adventures of P-chan and Learning the Hard Way primarily because they are Ryoga-centric and I dislike Ryoga. A few of them have Ranma-onna with a guy which I also do not like (Black Rose of Furinkan 4 for example). OOC books are pretty good because they are humorous. I don't much like Private Tutor Hinako because it portrays Ranma doing extremely poorly in school which is not something I like (my view on Ranma is that since he is both competitive and cares about how people view him he would not get terrible grades; though I also doubt he's getting perfect grades since has and does miss school). Miss Hinako and the Principal do not go after Ranma for doing poorly, they go after him because he does not conform, obey or respect them.
The book I looked at most recently was Queen of the Night (both parts), so I'll go into a bit more detail with it. The premise of the book I found to be pretty good, Ranma finds out Nabiki is working at a strip club. The art style is also pretty good (the art style for all the books is fairly decent). Like most hentai it has a weak plot and has the characters out of character.
Some aspects I can see the canon characters doing provided the right situation. For example, it's fairly believable that Nabiki would work as a stripper for cash; since it is shown she would do a lot of things for cash, morally worse than stripping, in the source material. That Ranma would strip itself is not all that out of character given a reason, considering he/she has no problem showing some skin to get an advantage in a fight, has very little physical modesty (has been told to put clothes on multiple time in both of his forms), has used his female form to manipulate guys, and likes being the center of attention. If Ranma will go through bridle training, while wearing extremely feminine clothing, to learn and defeat a martial arts style, coming up with a reason to get Ranma to strip, not all that difficult. Ranma going to/being at a strip club is, admittedly, fairly out of character, but given a reason is something he would do (he did end up in a love motel, girls hot spring, girls bath, sexy tea house,... in the manga).
A few out of character things were large enough to really annoy me though. For example, when Ranma gains admittance to the strip club via a fake I.D.; it has Ranma think *gulp* whoa this guy is huge and that he probably got that way from eating boys trying to sneak in. Ranma thinking that the guy is huge with the size of him intimating Ranma way ooc, Ranma in his smaller female form did not react that way to the Orachi, Pantyhose Taro's cursed form, or the Dojo Destroyer all of which were several orders of magnitude larger than that guy. If Ranma wanted into that place, or any place at all, Ranma would get in and not worry about the consequences (he could get in without the guy ever even seeing Ranma if Ranma wanted to avoid him, after-all Ranma can sneak up on people like Cologne, sneaking passed that guy would be simple).
With the given premise of the book, I'd think the story would go in a different direction entirely, instead of Ranma's female form being a stripper to help Nabiki. Ranma after finding out a big secret that Nabiki doesn't want to get out, I would expect Ranma to use, or at least attempt to use, that secret to blackmail Nabiki. Ranma has searched Nabiki's room twice looking for things that he could use against her in the manga and did attempt to blackmail her, finding something he could actually use against her would result in him using it against her.