I don't have the MASTER but the Solar Arcs is worth having. IMO, there is no better volume on Solar Arc Directions than Noel's. Additionally, you get Noel update to Reinhold Ebertin's COSI volume as an addendum in the back.
I don't use solar arc directions since I have a very weak Sun and IMO they don't work well for anyone with a weak Sun, but I would have the book in my library for use if I need it. Outside of his big pink, now blue in the second edition, book I think its the most useful of his books. Of course if you are a newbie, then rather than buying Rae Orion's ASTROLOGY FOR DUMMIES, look for on the used book racks and find Noel's seven volume set from the 70's. It is a real boon to your library, and a beginners Manual. Sepharials handbook is also good if you want to jump back two more generations behind Noel Tyl. That's pretty basic stuff and I sold my 70's copy to someone here on The Tyl Forum back in the 00's. Of course, Noel's cookbook for astrologers was really fun since it really was a cookbook rather than an acronym for one.