X-link to the Non-Fiction thread for some Mariner Books titles by sfnal authors:
@ $1.99 in the US only, Polish author Stanisław Lem's
A Perfect Vacuum, collecting his essays about imaginary books and related commentary topics.
@ $2.99 in Canada & the US,
Airman's Odyssey, a 3-book omnibus of French author Antoine de Saint-Exupéry's vintage aviation memoirs + novel based upon, containing experiences which influenced his classic
The Little Prince.
Also, the previously-linked Tom Shippey Tolkien biography
cum analysis has dropped to $1.99 in the US.