There is no way around it. Having your book properly edited is very critical to the presentation and acceptance of your book. 

When writing your book, your computer's spell checker is really your best friend, so select a very good one. You always want to do a spell-check on your document.  MS Word has a great one. Just remember that even the best spell checkers can not catch things like “I found the book over “their.”  The word "their" is spelled correctly but the proper word to use is “there.”

Also, don't forget to check your grammar and punctuation.  Your spell checker will help out here also.  Check your local library for a good simple book on grammar.  There is no need for you to be intimidated by this process; just remember that the goal of your writing should be clarity and conciseness. 

Once you have completed your editing, you should have someone else go over your work.  It is very difficult to find your own errors.  CB Publishing & Design offers:

Proofreading or basic copyediting - the identification and correction of typographical errors, punctuation errors, misspellings, and formatting inconsistencies, grammar, word usage, capitalization, word breaks, tone, and format.

Substantive copyediting - Includes clarity of subject, logic, and consistency. Confusing and awkward writing may be reworked. Sentences are analyzed for structure/syntax. Long sentences may be enumerated or separated. Repetitions (wording or writing patterns) are removed or highlighted for review. Proofreading, copyediting and substantive editing often occur simultaneously.