I had that same choice a while back in the airport, I went with Nemesis and it is excellent, though not quite as good as his book 'Armageddon' about the battle for Germany. You won't be disappointed with it, though I can't comment on Ambrose's book.
This book arrived today :
Ordnungspolizei - Encyclopedia of the German Police Battalions September 1939 - July 1942
by Massimo Arico.
Some parts of it go into great detail, for example Pol Btl 93 - I have photographs of 2 Graves from men of 1st kompanie, Res. Pol.Btl 93, both men died on 27 December 1941. From this book I discovered this level of detail :
There are other areas where there are massive gaps but overall I'd recommend this book to anyone interested in Polizei Battalions of WW2.
I ended up getting the Max Hastings book Nemesis. Brilliant read, would highly recommend it. Must get Armageddon now!
Reading Dalton Einhorns "From Toccoa to the Eagles Nest" at the moment. a fantastic book, self published too.
Current issue from "After The Battle" deals with the bombing of Dublin , might be of interest to folks.
If I might make a quick plug on a new guide to D-Day Beaches ;
"Walking D-Day" by Paul Reed (Pen and Sword) just published this month.
I bought a copy to take to Normandy (leaving on Wednesday), and having spent sometime with the book it is good.
The author Paul Reed is a well know author and historical adviser who has contributed to many good TV productions including "Dig WW2 Northern Ireland", which concludes on Monday night on BBC.
Paul is also a senior guide for Ledger tours.
Anyone going to Normandy , this is seriously worth packing to take with you, and is in its own right a good read.Publishers price of £15 , it can be had for about £10 on Amazon.
Friday next the fair at St.Mer Eglise and Sunday Tilly-sur-Seulles Book fair.