So all that I can remember is that the guy was a librarian working at library and it suddenly burned down and when he woke up he found himself in a world where magic can be used and he has all the books that was in the library in his mind and when he touches books they get stored in the library.
Well I know that it's not, "History’s Strongest Senior Brother" or "I’m Really Not The Demon God’s Lackey." Damn I thought for sure based if the thread title I'd know what you were looking for. Sounds interesting though I hope someone can identify it.
Library of Heavens Path (i think?) Throne of Magical Arcana (has magic qnd transmigation. Unsure about the library)
Definitely Library of Heaven's Path if he was a librarian. If not, Throne of Magical Arcana. I recommend the second one though, the first one is trash.