The Ebbs and Flows of Fortune by David Head is the one proper academic biography. There's also a popular book about the Howard family called something like House of Treason by Robert Hutchinson but I'm not crazy about him as a historian - he has a tendency to shove in totally unjustified descriptions of women in particular. However the background is pretty handy.
If you want novels there are a couple of entertaining but not totally accurate ones by D.L.Bogdan/Darcy Bonnette, Secrets of the Tudor Court about his daughter Mary and Rivals at the Tudor Court about him, his wife and Bess Holland his mistress. (Actually, she fucks up on really stupid things like having chipmunks running around, but the history on the second one isn't too bad. She just needs a good editor.)
What you really need to do, though, if you haven't already, is look for his letters at british-history.ac.uk. There are some real jewels in there.