Red Star Under the Baltic: a First-hand Account of Life on Board a Soviet Submarine in World War Two: by Viktor Korzh et al, pub. 2004.
The Naval War in the Baltic, 1939-1945 by Poul Grooss, pub. 2017.
And another even later published one I just saw here in a bookstore the other day, whose name escapes me now, but I was going to buy it when I realised I still had too many unread on my shelf. :-(
And of course a host of others that focus on the horrific accounts of the escapes, and non-escapes, aboard once luxury liners and lesser vessels, from the Courland Pocket in 45.