The ending was very underwhelming to say the least.

The novel in general was overall just average. The first third of the book deals with Darth Plagueis until he meets Palpatine. From there on it is basically a Palpatine origin story that leads into The Phantom Menace. Lots of characters show up: Dooku, Syfo-Dyas, Qui Gon, Maul, Nute Gunray, Ric Olie is mentioned and so on. Most of the plot is political manipulations by Plagueis and Palpatine. Hell, Palpatine even aranged for Padme being elected as Queen of Naboo.

A back story to a back story.