This set includes: 

The Admiralty Manual of Navigation Vol 1: Principles of Navigation, 11th Edition 2019
ISBN: 9781906915643

This comprehensive reference lays the foundation for safe and effective navigation at sea, including ocean and coastal passages, pilotage and anchoring. The fundamental principles of navigation developed over centuries of experience in the Royal Navy have been applied to the ECDIS era so that this new edition is 'digital by default'. The manual also contains essential guidance on techniques for navigating with traditional paper charts and for the operation of ships when GPS is not available. 

The Admiralty Manual of Navigation Vol 2: Astro Navigation, 11th Edition 2018 
ISBN: 9781906915582

Satellite technology enables almost every mariner to use electronic navaids to fix their position on the oceans. However, electronic systems can be disrupted by errors in a satellite or its ground control systems, defects in shipboard equipment or interference with satellite 
signals. The celestial chart therefore remains the most reliable tool for mariners navigating out of sight of land.

This new edition of the classic guide to celestial navigation has been redesigned for clarity and contains guidance on using UKHO/Nautical Almanac Office’s NavPac v4 software for astro navigation, including full-colour screenshots. With NavPac, a modicum of skill with a sextant and the appropriate chapter from the book, anyone can do astro.