The bigger the company, the bigger the buy, but also the bigger the bureaucracy. They will want to vet you and your book. If they find one thing that contradicts their image, company philosophy, or goals, they won’t buy the book. If they find other books more useful and appropriate, they won’t buy yours.
Corporations may also buy your book or use you as a corporate spokesperson if they can utilize you to help with their image in public. For instance, if your book discusses how to balance family and business life a company may want to show what a great corporate environment it fosters by having its employees get a copy of the book and also let the media know that they are adopting your suggestions. The media may then interview you about the book and your work with this company.
The key to selling to corporations is certainly timing, luck, persistence, and selling a useful book to the right individual at that company. But it also comes down to your approach. Just how will you present your book to the company?