A Blaster:
-Cannot scribe their own spell scrolls.(They can, however, still use spell scrolls that are scribed for them by others).
-Cannot create Magical Items.
-Cannot employ the use of Familiars.
-Cannot cast 4th or 5th level spells. They can ONLY go up to and cast 3rd Level spells.
-Proficient with Longswords, Short swords, Spears, Clubs, Daggers, and Crossbows.
-Can still Spellburn
-Has a 1D5 Hit Die
-Has a "Blaster Die" that goes up at certain levels and is added to their spell checks if I'm reading it right.
Compared to the Wizard, who is more a "scholar of magical mysteries or a power mad Archimage" the Blaster is mentioned more as a "professional arcane warrior."
So less wizard and more "Your a Blaster, Garry!"
Fluff wise, a Blaster uses magic via an ancient will driven spell tradition, originating in Greece, know as Spellweaving. Wizards can spellcast because they have the training/studying and Arcane Tomes to do so. Blasters pretty much can do it without having to dedicate the time or needing such arcane tomes thanks to Spellweaving.
Another fluff wise bit of note, in the book, makes it sound like that if you had a choice between sending a Wizard into a dangerous situation(Xcrawl) or a bunch of Blasters, you throw the Blasters into the meat grinder and keep the Wizard cuz a Wizard is a Wizard which is a valuable asset. Especially if you have a Qualified wizard which is a time consuming and expensive investment to even get/train.