Philosophy and Fun of Algebra by Mary Everest Boole is a compact and educational book that opens the reader to the joys of algebraic thinking.

In summary, Algebra is accepting one's ignorance, and solving the unknown is an angelic endeavor. (Angel meaning messenger in ancient Greek.) [1] To use mathematical terms, the previous comment would look like this:

• x = ignorance.

This book was published in 1909 and is a sound book for understanding what is algebra. I highly recommend it for its beautifully written style with analogies of problem-solving as a way to get closer to God. The book is roughly 50 pages long, and I am very sure that anyone can read it in one day - the challenge about reading is everyone can, but not everyone chooses to.