Tolkien. If you've never read it, you're missing out. Seriously, I could argue him as the GOAT (Other than the Bible, of course).
Right up there with him, Donaldson's 'Thomas Covenant, Unbeliever' series - at least the first two trilogies.
If that's all too heavy, Clive Cussler's Dirk Pitt stories are a continuation, a series, but each stands alone pretty well, and each is a simply written tale that is guaranteed to be a rollicking good time.
I really liked Anne McCaffery's 'Dragon Riders of Pern' for the story telling - Because it is different. They are short books, but in series, and a grand tale.
Likewise Paul O' Williams 'The Pelbar Cycle'
And of course anything by Louis L'Amour or Zane Grey if you like quickie Westerns. If you have't read the entire Sackett saga, it's good stuff.
Anything Ludlum.
Tony Hileman has a good series about Southwest Indian culture.