Paul Mular picked up the Hardy Boys Casefiles HARDCOVER 3 in 1 book at Borders.
It is in the “File Folder” cover style of the Digest books and uses the cover art of digest #152.
The Casefiles Stories used are:
Beyond the Law
Like the hardcover copy of the Digest 3 in 1 “Collector’s Edition”, this seems to be available only at Borders.