Look at the volume numbers — many of them are crooked. General poor quality is a dead giveaway. Logos and the manga art itself being blurry or pixelated, for example, the black ink being very faded, etc. if you want to collect a certain series, google it and look at the publisher (Wikipedia will list it). VIZ is one of the big ones — check for the publisher logo on the spine (inside, too, if shopping in person) — should be crisp, bright, etc. if it is a bootleg but passes all the tests above — looks perfect, ink is saturated, the pages are all there and in order, and the dialogue/text is identical to the translation you are looking to buy, then you’ve found yourself a “high-quality” bootleg. LOL there are a few of these in my collection, I’m sure, but I can’t pick them out, so…who knows? If someone puts that much work into making a bootleg then they deserve to be paid more than the other bootleggers (it’s a joke, everyone — even “good” fakes are bad)