Who is Time’s senior book critic? Not Lev Grossman, but his boss.
As far as I can tell, Lev Grossman is the only full-time book critic at Time, and its Literary Editor as well. His boss would be a senior editor, most likely Arts Editor Tim Morrison, or possibly Executive Editor Radhika Jones, who used to be the arts editor. Time is not known for its well-characterized hierarchy – titles indicate seniority and a certain level of independence, and not necessarily management or even editing duties.
That’s it! Radhika Jones is the name that I was looking for. Thank you, Nametag!