Reddit mentions of The Ancient Egyptian Coffin Texts (Aris and Phillips Classical Texts) (v. 1-3)

In general, R.O. Faulker's translations of the Pyramid Texts, Coffin Texts, and the Book of Going forth by Day are much preferable to Budge's ancient and inaccurate versions. Egyptology has come a loooong way in the past 100 years, and there's a lot of inaccurate, biased info in the old stuff that would distort the reader's understanding of just about every aspect of Ancient Egyptian religion. In general, the newer the translation, the more accurate it will be.

OP, other books I can personally recommend include:

The Complete Gods and Goddesses of Ancient Egypt Paperback by Richard H. Wilkinson

• Magic in Ancient Egypt by Geraldine Pinch
  
• Conceptions of God in Ancient Egypt by Erik Hornung
  
• Religion and Ritual in Ancient Egypt by Emily Teeter
  
• The Mechanics of Ancient Egyptian Magical Practice by Robert Kriech Ritner (you can download this online for free)

Would maybe start with an overview on underworld texts

Amduat and Amduat explained

Pyramid Texts

Book of the Dead (very large pages with full color plates of the Ani papyrus + translations)

Coffin Texts

Book of Gates and Book of Gates explained

Some of these may be available for PDF download elsewhere, if you search by ISBN.