Bill Bryson says in his introduction to Bryson's Dictionary for Writers and Editors that he has been writing for over thirty years. In that time he has had to look up a lot of words to see 1) how to spell them, 2) whether they mean what he thinks they mean, and 3) how to make them plural. He has also needed to identify many people and places. Being industrious and always thinking about another book to publish, he has kept all his research and created this unusual reference book with an abundance of small facts.
As a reference librarian, I do not really see an advantage to using Bryson's book over other works, such a the American Heritage Dictionary, but it is fun. (Of course, I actually find using the American Heritage Dictionary fun.) Occasionally, Bryson editorializes a little, such as letting you know that he thinks "snuck" is going to replace "sneaked," but he does not really try to be humorous in this work. Mostly, I just like seeing what words gave Bryson trouble. He too at some point had to look up "phenomenon" to check the vowels (I almost added extra syllables. I have sometime said "phenomenonanon.") If he has had to look up all these words, his accomplishments seem infinitely greater. Perhaps prospective writers can look at this book and say, "If Bill can overcome all this and write well, maybe I can, too."
Bryson, Bill. Bryson's Dictionary for Writers and Editors. Broadway Books, 2008. ISBN 9780767922692