Hello Felix,

If you are looking for memoirs translated in English, I am afraid there is not much. The only work that come to mind is:
"The Hunters and the Hunted" by Aldo Cocchia translation of "BETASOM, Sommergibili all'attaco" and this is not really a memoir as he writes about Italian submarines in the Atlantic. Cocchia was in command of TORELLI and brought his submarine to Bordeaux but then became Chief of Staff to Admiral Parona at BETASOM.
In Italian you will find several, to name a few:
"Sangue du Marinai" by Mario Leoni (C.O. of MALASPINA, first submarine to reach Bordeaux). This book has been reprinted in 2007 as "Il Sommergibile Malaspina à rientrato a Betasom".
Teucle Meneghini who was in command successively of several submarines in the Med during the war (though without firing a single torpedo at the enemy) wrote nevertheless a very interesting book "Cento Sommergibili non sono tornati".
The controversial Enzo Grossi (commanded MEDUSA, SPERI and BARBARIGO before being put in commnand of BETASOM) wrote "Dal Barbarigo a Dongo".
Mario Rossetto (C.O. of FINZI) wrote: "Missione "non attacare!" – Diario di guerra".
Add also "Le aventure di un marinaio di Betasom" by Mario Frandi and many others.
Biographies of famous commanders are also available: Todaro and Carlo Fecia di Cossato come to mind.
Etc.

Platon