Beginning in 1996, the copyrights for The Three Investigators series were renewed by Robert Arthur's daughter Elizabeth Ann Arthur, son Robert Andrew Arthur, and Random House. In 1998 the first eleven books in the series were re-issued in a paperback Trade Edition and a hardbound Library Edition*. The dimensions of this issue are about 7-1/2" X 5-1/4". New cover art for each title was created by Bill Dodge. The keyhole emblem on the spine and front covers has been replaced by the silhouette of a Sherlock Holmes-type character wearing a Deerstalker cap and peering through a magnifying glass. On the spine the Sherlock silhouette is placed midway between the top and bottom ends of the spine. Above it are the words "The Three Investigators" and below it the title of the book. Original retail price of this issue was $3.99 U.S. although copies could be purchased through various on-line retail bookstores at a discount.
The physical dimensions of the hardbound Library Edition are the same as the Trade Edition but there are differences in the design of the spines. Some of the Library Edition spines are plain as seen in the scan at left, others look like the spine of the paperback Trade Edition. There is also no "small print" information found on the front or rear covers of this Library Editon. Interestingly, the textblocks found in the Library Edition have the same ISBN's as the paperback Trade Edition but the ISBN on the back cover is a new one. The hardbound Library Edition retailed for about $12.00 at Amazon.com.
Scans of each of the eleven titles in this new format can be seen below. Based on the printing numberlines found on the copyright page and the type-face used in their manufacture, some of these books appear to simply be re-issues of the "Revised Keyhole Cover" while the rest are re-issues of the "Bullseye Edition". As such, these are not a new Edition of the series but a continuation of a previous Edition. The books feature Hector Sebastian and contain no internal illustrations.
By 2003 this format was already out of print and unavailable through either Random House or through Amazon.com. The paperbacks can usually be found online in used but good condition, the hardback (library) format is virtually impossible to find. Hopefully you got them while you could!
*My thanks to Jonny Nilsson for bringing this to my attention!