This book was surprisingly engaging and thoroughly well written. While I can't exactly describe it as suspenseful, I did want to know what was coming next, and would find extra time in my day to fit in a quick chapter.
Brands' use of short quotes interspersed with explanations or commentary works particularly well- he's able to use Grant's (or his contemporaries') words without disrupting the flow of Brands' language.
The second book, describing the Civil War and how it was fought and won, does a better job of describing the war than any other biography I've read (and probably most Civil War histories as well). I'll agree with Rich's comments that it could have used more maps, but in today's connected age, that's not so much of a problem.
Here's a typical passage that I think does a fantastic job of capturing Grant in a few sentences:

Grant thought it ironic that his visitors had come from a convention where at least one speaker had railed against the administration in Washington in the most vitriolic terms. “I have never seen a speech equal to it in malignity, vileness, falsity, and slander,” he told his visitors. He inquired whether any among them had refuted the slander. They said they had chosen to treat the speech with “silent contempt.” Grant puffed on his cigar, eyed them skeptically and sent them away.

One last random note- I learned the the "Rebel Yell" was the battle cry of Confederate soldiers (not just a song by Billy Idol).