I know this topic is very, very old, but I am playing the game again and was looking for the books, too. As I couldn't find any place listing all of them, I decided to continue this post.
It does appear that the books can be found in fixed locations, as I have always found them there and never encountered them randomly while reloading in front of a bookshelf. They are the large red book sprite and always look like they're very much treasured (usually lying on the owner's bed or very close to it), so in most cases, I leave them be. I've missed them in all my playthroughs, thinking it was always the same book (they do all start out the same). I only noticed after all these years and started looking for them. Here are the locations:
Volume 1: Aleroth abandoned house in the upper right corner (lying on a package next to the bed).
Volume 2: Cursed Abbey, the book is lying on one of the tables in the first library (upstairs, not the one in the cellars).
Volume 3: ?
Volume 4: ?
Volume 5: Farmland, the house belonging to the farmer with the refined taste for clothing. His house is located in the upper right of the farmland, next to stormfist castle. The book is lying on his nightstand (a wooden crate). (I found this and number 6 while reloading old savegames to figure out where I'd found Volume 9 - an endeavor I could have saved myself had I read the Themightyone's reply more carefully.)
Volume 6: Gleborus (dwarven village). South of the altar there is a dwarf looking for a lady friend who doesn't mind his intense scent. The book is lying on his bed.
Volume 7: There was, if I remember correctly, also a book somewhere around the house of the steward of Stormfist Castle, located in the top right, below the archery patch. I remember a chest behind his house, so this might be it. In my current game I haven't arrived there yet, but I think I'm going to take it, because (SPOILER) getting in there later is hard, and the people in the castle have been mean to me. Edit: I found some info I missed the first time around, in the lparchive. The book is indeed inside Theus' house, the castle steward. (And as it turns out, the location of all the books I listed so far can also be found there - oh well, finding them on my own was fun. I want to avoid posting links, but you can just google "lparchive Rivellon Reader's Digest". Pick the one about the gem.)
Volume 8: ?
Volume 9: Elrath's House on the lower right of the marketplace. You can enter it by picking up the key behind the house, after visiting his patients in the quarantine area. The book lies on a table inside his bedroom. I did take this one because (SPOILER) it would otherwise have been lost since you cannot go back there.
Volume 10: Orcland (lowest right corner of the first map, see Mitox' quest to poison the orcs' water supply). It is inside an orc tent lying on a bed. I took that one, too, because I kind of felt I'd earned it.
The 3 remaining ones should be at the places Rugster listed:
"Under the guild hall in archives in Verdist..
In thieves Guild..
In Sir dantes and patricks mansions."
And that should be all of them, I think.