NavList:

I concur with Frank Reed and Wolfgang Koberer re Hughes, Wright, and Blanchard;  I’ve not read Ristow.  There’s also ‘A history of Navigation in the Royal Air Force' published by the RAF Historical Society’. 

IMHO, Hughes is fine but is rather thin and doesn’t go much beyond 1946.  Wright is also fine, but it finishes abruptly in 1941 despite being published in 1971 suggesting that it might have started of as a university thesis, not that there’s anything wrong in that.  'A History of Navigation in the Royal Air Force' is available on-line as well as commercially, https://www.raf.mod.uk/rafcms/mediafiles/EEA1B9D1_5056_A318_A88B16BD35A68C31.pdf , so you can judge for yourself.  Hughes and Wright are available via ebay, but take your time, prices vary greatly.

Again, IMHO Blanchard is by far the best.  It’s made up of essays by acknowledged leaders in all aspects of air navigation and was published as recently as 2005.  There’s a very good paper on ‘Astronomical Navigation in the Air 1919 – 1969’ by J E D Williams.  You tend not to see SH copies advertised, but last time I checked, the RIN still had a few unsold copies hiding in a cupboard in their South Kensington HQ.  The cover price was £25, but by 2018 that might be negotiable.  I would email admin@rin.org.uk and make an offer. DaveP