Help:Screen:Verify

When a publication is displayed, there is a link in the left navbar labelled "Verify this Pub". Clicking on the link brings up the verification screen, which allows you to tell the ISFDB that you have verified some or all of the bibliographic information on the publication record. For more detailed instructions on how to use this function, see this help page.

Although Verification is useful, we'd appreciate you making the effort to add any other information you have about the publication, so Editing the publication might be more appropriate: and if you're not sure you have the same publication, then considering Cloning the publication instead. We would rather you come back and Verify information you ARE sure of than Verify a suspect or incomplete record.
Don't be afraid to question a previous Verification - the person that verified it is recorded and should have a talk page where you could, for instance, query whether the price was really $2,195 rather than $21.95: none of us are perfect editors.
You may just want to go into more detail than a previous verifier did too: a lot of collections don't have page numbers for every title for instance. Adding these doesn't add a lot of bibliographical detail but having the contents list in order makes it easier for people to spot a missing or additional story: in this case just add the page numbers and don't worry that you're messing about with a "Verified" publication.
If still in doubt, remember there are Notes that can be edited. So if you add a different publication because you're not confident that the existing publication record is right, you can still add your doubts as a note on the original publication: e.g. "my publication <give details or a link> appears to be a first edition but disagrees with the first publication date on THIS record".