I haven't read it either, but I love the film, and I thought there was no doubt that the commies were evil. It is implied that Lara ended her days in the Gulag.
Yes the events of that era were the background to a love story. It was a fascinating time as someone else pointed out.
There were a few more coincidences than one would expect in real life but I guess that is part of what made it interesting.
I also agree that Strelnikof was interesting. Maybe something like the old saying about power corrupting.