Justas,
Unless you have more money than I expect, or get a very good deal on a set of ABOK+and the encyclopedia (G+H), I would buy ABOK first and wait before buying the other.
I have both and find that I hardly ever take G+H of the shelf.
I have heard and read a lot of un-flattering nicknames for G+H, indicating that more knottyers think the same.
It is a great book portaying knotted work, but it is not as much a book of instructions.
Des Pawsons Knotcraft is a very good deal, not giving as much info, but being far cheaper, it should be your first buy, I think.
Willeke