I have 2 hard-copy sets of O'Brian's Aubrey/Maturin series, just in case of disaster (grin).
Lawrence Block's Matt Scudder series is good but he's losing focus lately and reissuing lots of his earlier, lighter works. Bah.
I like anything by Dick Francis, including the latest ones written along with his son.
Jack Whyte's Camelot series IMO is absolutely superb. I haven't tried his newer Templar series, but I have hopes there too.
For science fiction, try Jerry Pournelle and Larry Niven. Niven is not always my cup of tea (liberal California boy) but Pournelle is always good. Others in my library include William Dietrich, Jack Vance, A.E. van Vogt and many others whose names I can't remember and unfortunately their books are now packed up for our impending move so I can't check (grin). David Drake (another college English professor) is extremely formulaic but lots of his stuff is quite good IMO.
We've already mentioned Wilbur Smith, one of the very best. Also try Geoffrey Household's Rogue Male and The Adversary/Dance of the Dwarfs. His sequel to Rogue Male sucks so don't bother, apparently his worldview changed in his later life. Same with Leon Uris, his earlier works IMO are good but his later ones are filled with eastern-liberal politics.
Regards, Joe