Most of the Gakken books can still be had, but the Maru Specials are hard to come by.
If you're looking for references for IJN auxiliaries, there's not a whole lot out there, but I can make some recommendations for general titles.
Tamiya's Japanese Warship details Vol. 1 & 2. Out of print, but still readily available and affordable. Lots of line drawings of fittings, etc.
Lacroix and Wells -
Japanese cruisers of World War II - 600+ pages, definitive work, but pricey.
Jentsura, Jung, Mickel -
Warships of the Japanese Navy 1869-1945 - another definitive work, out of print, but still available.
The Japanese Merchant Marine in World War II by Mark
Parillo. More of a written study than a reference.
Japanese Naval Vessels at the End of World War II by
Shizuo Fukui. Excellent book, must have.
- Itani, J. & Lengerer, H. (1990):
"The Imperial Japanese Navy repair ship Akashi". Warship magazine 1990, pgs. 118-131.
There's lots of other stuff to be had if you're willing to poke around for it. Ebay (yes, I said it) is a great place to track much of this stuff down.
Jeff