Joe Haldeman is one of my favorite writers, hands-down. The Forever War is one of the finest books I have ever read. Go find a copy, and read it.
I just devoured Old Twentieth, and I am astonished by it. It's magnificent.
But it is very odd, also. The pace is not uniform, although it does increase its intensity. It wriggles with the surprising, chaotic, awkward twists and turns of lived experience, reduced down to a plot line. It is suspenseful, follows a single thread of plot... and still refuses to be tidy.
In many ways, OT may be better than TFW. (If you have ever discussed the latter with me, you will know how dazzled you should be by that statement.) That may be my personal bias, as cyberpunkish questions about learning, maturity, and sentience are a big part of my own writing and thinking at the moment and they form some of the central themes of this book.
I'm not going to do a full review. To do so might spoil it. I am going to tell you that if you like futurist fiction, reveries on mortality and melancholia, gritty war writing, and psychological science fiction, and particularly if you have ever been interested in cyberpunk concerns with nuances of sentience, you might want to pick this one up.