In fan fiction it is not uncommon for Ranma to start reading books or have him secretly read books, this is used to show his hidden intelligence often. In the manga, Ranma doesn't hide his intelligence and reads often. I'm not going to list every instance but here are some examples of him reading: While sparing with Akane, while waiting for Ryoga to show up before the Shi Shi Hokoudan arc, after figuring out the Moko Takabisha and waiting for Ryoga to show up again, reads dating magazines during the reversal jewel story arc, reading something when Akane made the edible curry, was reading before going to sleep during the time Miss Hinako stayed at the Tendo's (judging by the open book near him while he was sleeping), a manga at end of the master student pill arc, there is a picture Nabiki took of Onna-Ranma sleeping holding a book, etc. There are many more. Reading is one of the most common things he does, he certainly can be seen doing so more than playing video games (shown once in the manga versus Miss Hinako) or watching television (is only seen doing so while others are doing so, unlike Akane or Shampoo whom we see watch television alone).
Since I am a voracious reader it is an aspect of Ranma's character I easily identify with and makes sense to me for him to do so. Books are a means of acquiring knowledge such as martial arts (we do see Ranma turn to books for information in the manga), they are a form of entertainment that is portable (something he can do on his training trip when not training or while recovering from injuries), does not require electricity (many other forms of entertainment requires electricity and/or other people to participate with which Ranma would have had limited access to occasionally during his training journey), is easily accessible (books are not that expensive, libraries loan books out for free, people throw away books -in Japan Manga are released in phone book size magazines on fairly cheap paper that are not meant to be kept often times after people finish reading them they are tossed out and Ranma could acquire them by taking them from the trash or people giving them to him once they are finished with them), etc. I can think of a lot of reasons for Ranma to read often and I do not see reasons as to why he would not (particularly since we do see him read often).
What do you think Ranma reads?
Things I think he likely reads are:
*Martial arts manuals - at least one of the times it clearly is a martial arts manual.
*Text books - he is in school and we do see him carrying his school books with him often
*Researching a cure for his curse and other problems - would make sense since we do see him research using books - Dating magazines for tips on dating, a book on Chiropractics after Dr Tofu accidentally hurt Ranma, pressure point charts, etc., and since he wants to cure his curse books would be a good place to start a search.
*Cook books - Possibly at least for a recipe. In the manga he is a pretty good cook and likes to eat so this would make sense.
Beyond those he reads for entertainment. I'm assuming the manga he reads, if nothing else, is for entertainment. What genre do you think he reads? Personally I don't think romance or martial arts themed stories since he gets too much of that in his regular life.