Most of the books I read nowadays are epic fantasy. There is nothing I like more than to start a series where the books are 700 to 1000 pages long and there will be 10 or so books in the series. (Think Brandon Sanderson or Robert Jordan) It wasn't always like that though, when I was much younger science fiction was all I read.
As I believe I have mentioned before most of my childhood is lost to my memory, this the includes a number of the books that I read. Some titles however stick in my mind and they left a lasting impression and I can still remember the stories to this day.
The earliest books that I can actually remember reading were written by Isaac Asimov and they were part of the Lucky Starr series. I still have all of these books in paperback in my library. These books would compare most effectively to the Tom Swift (third series) books. Which I also remember reading though I liked Lucky Starr more. I first read these when I was 8 or 9, but I have re-read them many times since then and they stand up really well. Which is also not something I can say about Tom Swift (any of the five separate series).