Sometimes, yes, it is easy, but mostly it's kind of a pain. Let me give you a few tips for crafting a title that will make your editor happy.
Do your research
When trying to figure out a title for your book, research the market first. Find out which books compete directly with yours, and look for commonly used words, such as:
Those words are common for a reason, they provide insight into the type of book it is. You may decide to use one of these, and that's fine but it's just the beginning.
Frame the right tone
Many first-time authors try for a cutesy title, like Medication Marvels for a pharmacology book, or Is That a 301.4 or 568.7? for a medical coding book. Don't make potential purchasers guess what the book might be about, let them know immediately.
Sometimes, though, a cutesy title actually works. For instance, the title of our popular How to Survive and Maybe Even Love Nursing School is kinda cutesy but for the content and the author's presentation, it works really well.
By and large, though, stick with a straightforward title.
Ditto for the subtitle, if needed.
Keep it short and sweet
Short titles are almost always best for a lot of reasons, but mostly because they're easy to design around and they stand out to purchasers because they're easy to remember. In healthcare publishing, though, we're often publishing for a specific market, so sometimes long titles can't be helped. For instance, "pharmacology" and "medical assistants" might both need to be part of a title. That's fine, because potential purchasers will look for those words to know about the book. Just don't hide them in a bunch of other words unless it's absolutely necessary.
Make sure that your title is search-friendly. Think about the last time you looked for a certain kind of book on Amazon.com. Let's say you're looking for a pharmacology book for allied health students, and you typed "pharmacology allied health" into the search box. You probably got back mostly titles that have those words in the title or subtitle. You might not have seen Medication Marvels in the results because it didn't have "pharmacology" in the title.
That's why we publishers often use a fairly long subtitle, so searches on Amazon and other distributor websites will include the book in their results.
The title "decider"
The good thing for textbook authors is that the final decision about a book's title doesn't belong to them anyway. It belongs primarily to the acquisitions person and ultimately to the company itself. That's because the title is a marketing and sales tool more than anything else.
One more little thing
Before I let you go, do me a favor. When you tell people what your book is called, don't say, "My book is entitled Such-and-So." It's not entitled, it's just titled.