G penned numerous books or booklets, but there are three that are the main ones:
Meetings with Remarkable Men
This is designed to be read first. it is by far the easiest. It's intent is to posit a different purpose to life and our desire for achievement. This is very important, as even those of us who have spiritual yearnings are still loaded beneath the weight of the world's purposes. In this book, G demonstrated a dedication and single-mindedness of a group of aspirants, many of whom never made it to their goal.
It shows to those who first come upon the path, that there are some who take it extremely seriously, and align their full commitment to attaining real knowledge, yet still don't find it. That the way to reaching real knowledge is long and difficult, plus we have to drop most of our first enthusiasms, and only after despair and sustained effort will the doorway open. Real knowledge is not something we can demand while drinking a beer and watching TV.
Beelzebub's Tales to His Grandson: All And Everything.
This is his primary work, and took him a long time to write. He wrote it twice. The first version he scrapped because it didn't work. G used to have parts read out to an audience, while he watched the audience. The first version explained what he wanted to say, but it was too clearly written.
G discovered that unless a person is under some stress, any info that goes in is not worth much. This is the same principle as birth pains. We humans have a habit of not valuing anything we haven't paid for. So he re-wrote the book making it extremely difficult to read. That way he was able to get the reader to exude the correct energy - this type of energy can only be produced when a person seeks essential truth through great effort. It was the production of this type of energy that he realised was necessary for the future evolution of the planet, or it would settle for masses of lower energy which it could get from wars and famines. This is all tied up with the laws of compensation.
The other purpose to Beelzebub's Tales was to demonstrate a new way of thinking, and to inculcate this deeply into the reader. He wanted to obliterate the old thinking which we are brought up to in the world. Then to replace it with new neurological pathways.
Life Is Real Only Then, When I Am
This was to be read last, once the reader was thoroughly familiar with his view of existence and its meaning.
There are other booklets which he produced earlier in his journey, and they are also very interesting.