I think most would agree to start with George Anastasia and branch out from there, but I do feel that most of his recent work is a little more regurgitated...or maybe there was just so much more action in the 80s. Blood and Honor is in my all time top 10 (not just Philly LCN), and Mobfather is also very good. I would also recommend The Plumber (Salerno/Rivele), Mafia Wipeout (Cox), Breaking the Mob (Friel/Guinther), Blood Oath (Fresolone) for more on the Scarfo era. Leonetti's book Mafia Prince is enjoyable despite the shoddy writing/editing. From a slightly different perspective, Robert Simone's The Last Mouthpiece is a decent read...he was a longtime attorney for Scarfo and other LCN figures.
For much more historical Philly stuff Celeste Morello's Before Bruno 3-parter is just okay, but you will likely do better reading old PCC reports from the 80s for stuff on Little Nicky. And on another tangent altogether Sean Patrick Griffin's books on Philly Black Mafia/JBM and its connections to politics/industry/LCN from historical to current day are pretty comprehensive...I only wish this guy wrote more about LCN as his material/details/sources are top notch.