Hi James, the list I would have is
Webb Society Deep Sky Observers Handbook Vol 2
Night Sky Observers Guide Volume 4
Hynes Planetary Nebulae
Wallace – Visual Observations of Planetary Nebulae – available from Webb Soc
Hartung – Astronomical Objects for Southern Telescopes.
Cosmic Butterflies – Sun Kwok
Eicher – Deep Sky Observing with Small telescopes
Webb Celestial Objects for Common Telescopes
Smyth – Bedford Catalogue
Deep Sky Wonders – Houston
Could not recommend
Planetary Nebulae and how to Observe Them – too many errors.