Hi, someone here ready to use this old (but very good!) book as my main reference in my repertoire (occasionally, I'd have to say). The few times I am going to use 1.c4 in important games it's not worth to get a massive "up-to-date" repertoire source. This one is perfect because it's direct, easy and to the point.
Any major change I would have to consider? At my level of opposition (mainly <2000 fide OTB) I don't expect great refutations, I only want playable games knowing plans, typical structures, pawn breaks to accomplish, etc. I basically want to use the 1.c4 e5 part (part 1 if I am not mistaken) and some ideas in the part 3 (other responses but 1...e5 and 1....c5).
Right now I am using it exclusively in blitz (all my games start now with 1.c4), and getting good positions. I am in training mode

My two main concerns (in advance) would be the c6 systems (2...c6 / 3...c6) and, mainly and basically, the e5-Nc6-f5 complex (trying to double my pawns with Bb4 and Bxc3). Happily for me, not seen in any single game. Very few 1.c4 e5 games, btw. Lots of 1.c4 Nf6 and 1.c4 c6.
thx !