about

about and on

On is used to suggest that a book , article , lecture etc is serious or academic..

About is ususal for general or.. more casual.

a textbook on African history; a book for children about Africa.

about to

means 'going to very soon'
Don't go out now - we're about to have lunch.

above and over

1. About and over can both be used to mean 'higher than'
but when the meaning is 'covering' and 'crossing', we ususally use over.

The plane was flying over Denmark

2. with number, and expressions of quantity or measurement; it is more common to use over ( = "more than")

There were over 100,000 people at the pop festival.

3. But above is used when we think about measurment on a vertical scale. (up and down)

The temperature is three degrees about zero.

4. Combine of above and over

The summit of Everest is over 8000 metres above sea-level.

5. Note in a book or paper, see over means ' look on the next page' ; see above means 'look at something written before'.