Capture a theme about which you are passionate. Since inspiration intertwines with emotion, plucking the heartstrings is essential. The resounding theme can be classically evocative, as with justice and revenge in "The Count of Monte Cristo." In contrast, Ayn Rand's writings, specifically "Atlas Shrugged," inspired many to an individualist outlook on life.
Refine the balance between sparse style and excessive repetition. Touching upon the theme or a related inspirational material---a character's triumph over adversity, for example---only once or twice over the length of a book will result in too much bland description. On the other hand, an "inspiring" action or drama event in every sentence would be overkill. Text needs to develop a plot and rationally connect inspiring moments with dialogue, character development, exposition, and so on.
Flavor the book with a personal touch, since inspiring literature is already plentiful. Readers may be inspired to a steely professional integrity after reading Rand's work. Alternatively, they may fancy a simple life after absorbing Thoreau's "Walden." There are few themes left unexplored, so it is your uniqueness that will help your distinguish your book from others. Do not fight your voice or style, and do not try to be everything to everyone. Inspiration does not have to be formal or flowery. If you are dramatic, be dramatic. If your writing style is direct, circumspect, profane, genteel, etc... Write accordingly.