The A-26 Invader was the successor to the war-winning A-20 Havoc. Unfortunately production issues delayed its introduction and it therefore played only a bit part in proceedings. This video charts its development and war service.
Sources:
Osprey's "A-26 Units Of World War 2" is the usual fare - a short read and light on technical details, but containing good stories. It is also quite affordable and readily available
The best book (in my opinion) on the A-26 is "Douglas A-26 and B-26 Invader" by Scott Thompson. It has a wealth of technical detail but is a harder read and slightly oddly laid out in parts
"A-26 Invader In Action" by Jim Mesko is a nice short read and has excellent line drawings of significant components by the peerless Don Greer
"A-26 B/C Invader" by Francis Gallemi is a little hard to find but also has nice line drawings and schematics. Not so much text in this one though
Detailed service records from the ETO combat trial can be found here: www.416th.com/A-26-ETO-CombatEval/A-26-ETO-CE_AirCraft.html
A great deal of detail on Invader weapons can be found here: https://www.claybornglobal.com/IHF/index.php/Invader_Weapons