Are their other books I MUST read before reading Honor Bound? So I get all the references?
There's nothing you
must read because
Star Trek novels are a luxury item and are not required reading.

I also made an effort to fill folks in who might not have read earlier books or simply might have forgotten details. Having said that,
Honor Bound is part 2 of a two-part story, so I'd recommend starting with
A Good Day to Die.
Here's the full list of significant appearances by Klag and the gang:
"A Song Well Sung" in
Tales of the Dominion War
TNG: Diplomatic Implausibility
The Brave and the Bold Book 2
I.K.S. Gorkon Book 1:
A Good Day to Die
I.K.S. Gorkon Book 2:
Honor Bound
I.K.S. Gorkon Book 3:
Enemy Territory
"
loDnI'pu' vavpu' je" in
Tales from the Captain's Table
Klingon Empire: A Burning House
A Singular Destiny
Are there any hardcover/collector versions?
Nope.
Hope you enjoy the books!