I'm passing along second-hand knowledge, not firsthand, so take it at face value and consider what others have to say. My best friend at school is the librarian, and this is what I know from her. It's true that there are no papers to grade or report cards. There is contact once in a while with parents who can be crazy and unreasonable with the librarian as well. She's had people wanting her to remove books from the library, or parents trying to replace a hardcover-bound book with a cheap paperback version instead of paying the $20 owed. She has to schedule 20 teachers at 2 library times per week, one for a lesson which usually involves a read-aloud, and one for book checkout.(our building is 2nd and 3rd grades) She has to deal with 20 teacher personalities, which can be difficult or not, depending on the year. She has to complete reports on the library, about circulation, how old the books are, what types of books, etc. There are state (or fed?) standards that everything must snap to. She has endless shelving of books to do. She has teachers who send students 10 at a time to use the library when another class is in there. She has extended contract, which means she works 2 full weeks later than the rest of us doing her inventory for year-end. She also starts 2 full weeks before the rest of us to prepare the library for the first day of school. The library is always being used for meetings, before and after school, and she may or may not be informed of it.
My friend taught in classrooms before this, and she prefers the library, but she is passionate about reading and books. In our state it takes a special certificate or endorsement, which can be done within the 2 years they give on a provisional. If this move is also right for you, I say go for it, and enjoy!