Preparation: Decide on your topic, do your research, and create an essay outline.
Writing: Set out your argument in the introduction, develop it with evidence in the main body, and wrap it up with a conclusion. Revision: Check the content, organization, grammar, spelling, and formatting of your essay.

Hi Prissy,
There are a number of books on essays but I will suggest you not to confine yourself to a book only. Please make researches on a selected topic from various resources like google, youtube, newspapers, articles, etc. Some essay topics are current affairs. I consider studying "The Dawn" newspaper on daily basis.
However, you can consult these books as well.
A Professor's Guide to Writing Essays,
College Essay Essentials
The Only Grammar Book You'll Ever Need
The Art of the Personal Essay etc.
Thanks
Best Regards

I also use some of theese sources to study about writting essays