Who Is Buried In Grant's Tomb? And Who Wrote Margaret Truman's 'Capital Crimes' Murder Mystery Series?

I don't know and can't tell you the answer to the first question. But as to the second, I'm increasingly confident the answer is Donald Bain, perhaps in collaboration with Ms. Truman, or perhaps solo. In any case, since Ms. Truman's death, Donald Bain has been writing and publishing new novels in the same series. It surely is good to revisit Mac and Annabel!