Oblivion Glitch.. D:

hey, i have found what i think might be a glitch in the game Oblvion. The thing is that, i didnt do all of the quest "The Path Of Dawn" because of this before but, i was not sure if it was a glitch at the time. so i got to do alot of sidequests. i mean ALOT. and now when i did the path of dawn this is what happens.

i finished all the previous little quest for th path of dawn. and so now i need book of commentaries 3. the bookseller says gwinas has it. i go to the hotel and...
after he is surprised about the cult. he stops talking and.. well, he doesnt give me the book. now i cannot even get to that. he wont even let me talk about the book. what can i do now? i dont want to reset my charecter!