I've seen it both ways. I haven't counted to see which is more common. I have seven books in easy reach and none have the word "by" before the author's name. One does have a title, the authors' names, and then it says "foreword by Grady Brooch".
I think it's a good idea to include the "by" if there is possible confusion about whether this is the name of the author. For example, if the title is a person's name. If the cover says "Sally Jones ... Mary Smith", is that a book about someone named Sally Jones by a writer named Mary Smith, or a book about someone named Mary Smith by a writer named Sally Jones? But if the cover says, "Calculus for Engineers ... Fred Stover", few will think this is a biography of Fred Stover by Mr. Engineers.
There could also be an issue if you have an unusual name or a foreign name. (Foreign to the language in which the book is written, I mean.) Like if a book's cover said "History of the Punjab ... Ananda Khan", an American reader could be forgiven for wondering if "Ananda Khan" is the name of the author, or if the book is about a ruler of the Punjab called "the Ananda Khan". "by Ananda Khan" would eliminate any question.
As I write this, I see your name is "Javeer Baker". If you wrote a book about cooking, I could see a possible ambiguity. Like, "Cooking in the Outdoors ... Javeer Baker". Is Javeer Baker the author's name, or is this about some new kind of backyard grill called an "Outdoors Javeer Baker". :-)