The two books by Richard Dolan 'UFOs and the National Security State'; he's a trained historian and takes a very thorough and measured point of
view towards things; there was a lot of FOIA releases during the Carter era and that's when he got some or most of his information. He seems to vet
things as well as anyone can.
You'll find there are always people debunking books and movies about Roswell and the rest of it; you really have to make up your own mind. Even
Corso's book has been called the rantings of someone on their deathbed, which hardly seems likely.
You should try reading something on either Area 51 or Roswell. The two are not connected- not in reality anyway.
For Roswell, try UFO Crash at Roswell by Saler, Benson and Moore.
For Area 51, try Dreamland by Phil Patton.