From what I understand based on discussions elsewhere, this is the first mainstream print publisher to release their entire frontlist catalogue in electronic format:
Harlequin Joins the E-Book Side
By Josh Kerbel -- Publishers Weekly, 9/21/2007
Harlequin said yesterday that from this point forward it is making its complete frontlist catalogue available in e-book format. Active in the e-book marketplace since October 2005, with an initial publication schedule of nine titles a month, Harlequin will now be releasing more than 120 titles per month in both print and digital formats.
Harlequin’s e-books will be priced slightly lower than their print books and be available in Adobe, Microsoft Reader, MobiPocket, Palm and Sony formats. The company said it is launching this initiative because its customers embrace the immediacy and portability of the format and the titles do not go out of stock.
This isn't the only lead Harlequin is following from erotic/romance e-pub. Taking their cue from Ellora's Cave's Quickies, Phaze's Heat Sheets, and Red Rose's Petals, Harlequin is now releasing short 'n' spicy quick reads:
It's like watching what happened back in the early 90's with alternative music and small label indie bands. Very very interesting developments indeed...