Everybody wants to have written a book, but nobody wants to go through the trouble of writing one. For the average person, writing a book is not easy and could even take years. However, if you have at least a little writing talent, writing a book in just 100 days is possible and simply boils down to a mathematical equation. Before you start, however, it is important to decide what kind of book you plan to write and be realistic about your expectations.
Choose your book topic, genre and set realistic goals. For instance, unless you are a prolific typist, it is probably best not to attempt a 1,000-page Lord of the Rings knockoff. On the other hand, don't make the mistake of thinking that 100 days is more than enough time to become the next Dr. Seuss and knock out a twenty page illustrated children's book that gets adapted into a beloved Christmas special, which airs annually.
Begin to write. The very first day of that 100 days is by far the most important. Believe it or not, the first day is the day you are most likely to give up. For that reason, there is only one thing that must be done on Day One: get words onto paper. Preferably, you should get at least one full page done. For the average adult mainstream book, this means just 300 words. These 300 words don't need to be prize-winners, and they don't even need to be in use on day 100. In fact, most likely you will have gone back and rewritten all of those 300 words, so try not to worry about them too much.
Those 300 words you put on paper the first day then become the template by which you can expect to finish a good-sized book in 100 days. If you can produce just 300 words every day for 100 days that equals 30,000 words or 100 pages. That is longer than the average how-to book, considerably longer than the average children's book and the standard length for a novella.
Realizing that you need to only write one page a day in order to achieve a perfectly fine length is the secret to writing a book in 100 days. Attempting to write an average length mainstream novel means you need to only write 800 to 1,000 words a day. A mystery or romance novel can be written in 100 days by churning out just 400 to 500 words a day. Approaching the act of writing a book from the perspective of a daily output goal is the key to not being overwhelmed by the thought of actually completing a book in just 100 days.
Writing a book in 100 days is an endeavor that depends as much on commitment as it does on talent. A fairly talented person who makes sure he puts out this 300 words a day will finish a book in 100 days. A more talented but less dedicated writer may miss a day here and weekend there and will not achieve his goal. Set your daily goal, and do no let anything less than a genuine emergency get in the way of meeting that goal.