I know it is just a work of fiction, but have you Lincoln by Gore Vidal? It really is a wonderful book and Chase plays such a big role in the book as does Seward. Vidal paints an excellent portrait of Lincoln.
I can’t seem to bring myself to read anything by Gore Vidal. No doubt it’s my loss, but there it is.
It paints an excellent portrait of Lincoln only if you think of him as a blood-thirsty tyrant and dictator. If you're looking for a better fictional representation of Lincoln and the other leaders of the time then I would recommend "Freedom" by William Safire. Not only does it give an interesting portrait of Lincoln, and unlike Vidal's work Safire had end notes giving his sources and reasoning for each of his chapters, but it gives a fascinating portrait of John Breckenridge.