If you like that book, you might find her other books that center in and around that particular period in time (1180 - 1230s), with emphasis on the Marshal's contemporaries; there are two that feature him, the one you mention which deals with his earlier life, and then there's the Scarlet Lion, which deals with the second half of his life, up until his death.
The duology of For the King's Favor and To Defy a King deals primarily with the Bigods, Roger in particular, and later his son Hugh (who marries the Marshal's eldest daughter, called Mahelt in the books) which were also very good reads. Having never experienced true medieval life, one can only go on what references that have been passed down thru the ages - but her prose seems to capture what it might've felt like to live back then.
I just got a teaser on a new book of hers called The Outlaw Knight which deals with Fulke Fitzwarin, yet another Marshal contemporary (the novel begins in 1173, when the Marshal would've been about 27 years of age); will probably pick up the Kindle copy after I finish Outremer, by Richard Allibone (a rousing good read if you like anything to do with the Crusades).
I had recently read The Winter Mantle, also by Chadwick- set in 1066; I need to read it again because I don't recall much of it.
If you're a fan of medieval fiction, you might want to have a look at Bernard Cornwell and Stephen Lawhead; as far as I'm concerned, the two of them are equal to Chadwick in most areas.
There's also
