If you feel like you've got the wrong tone of voice, don't understand the ins-and-outs of grammar, or just don't feel confident writing about yourself without sounding like an idiot, read this book.
Copywriter Tait Ischia is brief and to the point in an interesting and engaging way. Which is exactly what you want the words on your website/marketing stuff/professional bio to be too, right? Feel confident in what you say and how you say it when you put fingers to the keyboard. Waffling on should really be reserved for weekend breakfast.