Skill training & mindset are sometimes over looked for armed citizens or armed professionals(security sworn LE military EP specialists PIs etc).
Owning firearms & knowing how to use them are different issues.
In general here are a few non-fiction book titles to aid gun owners/armed professionals;
NOTE: some titles or book edition content may have changed or the author names may be wrong.
No Heroes(the start & organization of the FBI's elite Hostage Rescue Team/HRT), Cold Zero(about the HRT & how the FBI trains snipers/SWAT tactics), First Seal by Roy Beihm(the US Navy officer who helped train SEALs & UDT ops), No Second Place Winner: Bill Jordan(a top level shooter who served in the US Border Patrol & was a WWII combat veteran), Stressfire & In The Gravest Extreme by Massad F Ayoob,
www.massadayoobgroup.com , Rogue Warrior & Red Cell by Richard NMI Marcinko,
www.dickmarcinko.com , Dead Clients Dont Pay & The Bodyguard Manual by Leroy Thompson, Delta Force by COL Charles Beckwith(the US Army officer who created the elite SFOD-1/Delta Force), John Plaster's books about the elite spec ops unit; MAC-SOG(Special Operations Group or "Studies & Observations Group"), Robert Boatman's Living With ... series;
www.boatmanbooks.com , No Lights No Siren(about the NYPD by a highly decorated officer), On Killing & On Combat by LTC Dave Grossman(a retired US Army officer who researched death-PTSD/killing), One Ranger by J Jackson(a retired Texas Ranger & NRA board member), Inside The Delta Force by CSM Eric Haney(US Army-retired), One Perfect Op by Dennis Chalker(retired US Navy specwar & plank owner of SEAL Team 06), American Sniper by Chris Kyle, KBL by John Weisman, Special Forces by Tom Clancy, Bravo Two Zero by Andy McNab(about counter terrorist units & the elite 22nd SAS Regiment), Talk To Me(about hostage-crisis negotiators in the elite ESU; Emergency Services Unit New York City).
Other good gun & tactics related books include; Clint Smith, Elmer Keith, Jeff Cooper, John Farnam, John Shaw(Mid-South), Jim Cirello, Lewis Aleback,