yup, and the original app to read these was MobiPocket reader. Curiously, the pdb wrapper is completely pointless on all non-palmOS platforms, but since it only

yup, and the original app to read these was MobiPocket reader. Curiously, the pdb wrapper is completely pointless on all non-palmOS platforms, but since it only adds a negligibly-small header (0x4e + (dataSize / 0xff00) * 8) bytes, nobody cared and it allowed using all original tools