Probably the first Science Fiction Book that I ever read was Spaceship Under the Apple Tree by Louis Slobodkin. Today, SFSignal.com pointed to his personal website. Yesterday was his birthday (he died in 1975). I shocked the librarian at Hilltop Elementary School in Nyack by asking for more spaceship stories. What she showed me was a shelf of books that include Heinlein as well as other juvenile SF. My favorite was “The Planet of Mist” (Misty planet? – something like that), which was a story about Venus and a spaceship that crash lands there. I wish I could find the book.
I liked Spaceship Under the Apple Tree and its sequels because I had an apple tree in my backyard, and the locale was obviously the Hudson Valley, so it was quite possible that one summer evening I might discover a spaceship under my apple tree.

Note: I did a search and discovered “Flight to the Misty Planet” by M. E. Patchett. The book is out of print and it goes for about $200 everywhere. I have added it to my eBay search list. It’s the story of two boys who get stranded on Venus and the cool time that they have before they manage to repair their spaceship.