His books are pretty decent. They're pulp fantasy but in a more interesting way compared to other pulp fantasy. Chaos is still often depicted as a villainous force in them but it's less cut and dry compared to his derivatives. Particularly since Order is also included as the opposite and isn't presented as being (that much) better.

There's also a lot of them, I'd recommend reading a synopsis of each main story he wrote then picking the one that interests you the most to start with. They're all mostly self contained but he also popularised the use of multiverses in fiction to do some crossovers between the different series.