Blue's Clues - What to Do Blue? (lost Nick Jr. Audiobook Cassette; 1999)
What To Do, Blue? is a book and audio cassette combo released on September 14th, 1999, according to the allmusic.com page, which is also notably one of the VERY few sources for information on the release. The original book alone was released somewhere in June of the same year. The book itself was created to tie in with the Blue's Clues franchise, and the audiobook/cassette notably featured narration by the series' co-creator, Angela C. Santomero.
Availability
The book by itself is readily available to buy on multiple e-commerce sites (namely eBay) but currently it seems nigh impossible to find any listings online for the cassette combo release, or even just the cassette by itself, this is presumably due to low sales due to not being very well advertised or known about, apart from those who owned other select Blue's Clues CD's, although it may have been advertised in elsewhere.
It is currently unknown if there were any commercials or anything of the like to promote the Tape and Book combo apart from advertisements in the booklets of CD's, although it is unlikely.