You need this book. No, seriously, if you've ever suffered through tedious presentations, with slides packed with text of font size 8, with a presenter reading their slides, or if you've ever committed such abominations yourselves, you MUST read this book.
The book is really well done, covering all the aspects of presentation work (and yes, it is work), from early planning to presentation. But Schwabish organizes presentation design around three principles: visualize, unify, focus. All three principles organize all the chapters and every aspects such as choice of colors, fonts and type, text, data visualization, images, and scaffolding.
The book also comes with a website that is chock full of resources, so, bookmark it as you read.
Also, I pretty much guarantee that not only will you read this book cover to cover, but you'll come back to it every time you have to design a presentation (and have it at hand at all times) or you'll grind your teeth every time you have to sit through a presentation that "violates" all the advice given there.
Highly recommended.