My XX-blessed friends are very fond of anything by CJ Cherryh and Joan Vinge (especialy her PSION novels) but they prefer *good* SF, the kind that appeals to anybody with taste.

Along those lines I would suggest 1632 by Eric Flint, anything by Lois MacMaster Bujold (but if you want to start somewhere, CORDELIA's HONOR or CETAGANDA are excellent starting points), and David Drake's RCN novels (WITH THE LIGHTNINGS at a minimum).
My mother is a fan of all three series. (As well as the Honor Harrington series.)