<p>a lot of the time, custom books are hardly different from standard - they usually switch things around or omit certain chapters. this depends on the class and professor. (and no, lab manual = lab manual, custom textbook = modified version of the standard textbook)
i would just get the standard because it’d be a lot cheaper and just use someone else’s book if i find i need to, but you might want to ask the professor first to figure out what exactly is different between the books.</p>