In the fantasy genre Eddings has written 4 series The Belgariad, The Malloreon, The Elenium and The Taumuli, 2 prequels Belgarath The Sorceror and Polgara the Sorceress, a compilation of his research notes for the world of the Belgariad The Rivan Codex and a stand-alone fantasy novel "The Redemption of Althalus".
His style is humorous and fluid, particularly in the dialogue between characters, with realistic banter which makes his characters more engaging and beleivable than extended description would do. Often criticised as being unoriginal and a formula writer, a perception not helped by the fact that all four series contain a very similar cast of characters, and an oddly familiar plot.
It is important to note, however, that when first published The Belgariad marked a departure from the formula fantasy of the time, which was firmly rooted in Lord of the Rings. His wizard was not a distant puissant and aloof character, all knowing and all wise, but an irritable rogue, given to boozing, wenching, lying and theft. The light-hearted tone of the series made it a breath of fresh air amongst the often turgid fantasy of the time, without being as juvenile and specious as Piers Anthony
He has tended to milk it to death since though.
His most recent novel, Regina's Songis a crime thriller - I haven't read it, so can't comment - it would be nice to think it marked a return to mainstream for Eddings, since his two mainstream novels "High Hunt" and "The Losers", both written in the seventies/early eighties are quite different. "High Hunt" is a journey of self-discovery for the main character, a recently released G.I, and "The Losers" a dark and compelling examination of life on welfare and how the social services system affects those caught up in it. Both these books were written before the publication of The Belgariad, but did not achieve any notable success until later.
"The Losers" is probably Eddings at his best, showing his ability in characterisation, plot and his often dry wit