Went on 6 dates over 2 weeks, he introduced me to his friend. I also slept over night but we didn't go all the way. Last time I saw him at his place I saw a book that interest me he said I can take it home to read it. When I wasn't looking he put the book into my handbag to make sure I take it.
From your description, it doesn't sound like he doesn't intend on seeing you again... Six dates in two weeks is pretty significant. Plus meeting friends is a good sign too. Something may have come up, you never know.
Send him a text telling him you've finished it and would like to return it over dinner or something. If it is over, write a cute note and put it inside the book hoping he'd find it. Like in that film Serendipity with John Cusack & Kate Beckinsale.