Horace Beam Piper of Little Fuzzy, Space Viking, and Paratime fame is probably the best SF author I know of - he knew how to put a lot of story in relatively small package.
The fantasy book, possibly the best fiction book ever, is Silverlock by John Myers Myers. He wrote some other stuff, but nothing else nearly as good Silver lock.
The rest is just the usual stuff of a Space Opera fanatic:
Robert A. Heinlein
David Weber
“Doc” Smtih
Steve White
Travis Taylor
etc.
Two other great fantasy books:
The Princess Bride by William Golding
The Incompleat Enchanter series by Fletcher Pratt and L. Sprague deCamp
Had Pipers Little Fuzzy long ago but loaned it
out and never got it back,nobody returns a loaned book.
Great cover art it had,that teddy bear holding
a pitchfork.
Van Vogt wrote some great SF,too bad some of the
early writers are not being printed more often
On your recommendation, I took the book on vacation. It was a pretty good book. If it had been written twenty years later I'm sure Shandon would have shared some Lembas bread with Frodo and Samwise Gamgee.