In the late 1950's and early 1960's our parents gave us lots of books. We also liked book series that we could regularly add to our collection. I collected Tom Swift Jr. books which were science fiction adventure tales. Betsy read the Nancy Drew detective series and Tom read the Hardy Boys detective series. Cathy had the Bobbsey Twins books and I'm not sure what Rita and Dan read. There was a series of farm and forest animal characters around the house.
I got started on Tom Swift because I had some hand-me-down books from Uncle Charlie. These were from the older Tom Swift series that were published throughout the 20's and 30's. I read those and then started on the new series that started in 1954 and went through the 60's. I probably had a little over a dozen of those books. I was reading the Tom Swift books from about fourth grade right up through early high school and they started me on my lifelong love of science fiction.
I was also reading the Tom's Hardy Boys and occasionally read some of the Nancy Drew books. Never read any Bobbsey Twins.