The Hardcore Novels Special Editions are an omnibus of The Hardcore Series. 

Untouchable Billionaire dimensions: 6 x 0.97 x 9 inches - 430 pages 

Unstoppable Billionaire dimensions: 6 x 1.12 x 9 inches - 496 pages

Unforgettable Billionaire dimensions:  6 x 1.24 x 9 inches - 548 pages