question about tie in comics

I’m reading crisis on infinite earth right now and I noticed the series is 13 issues long but the collection is many more.

Are these what people call tie in comics? Are they in order on the collection tab? And an I missing anything my only reading the 13 issue main story? Thanks to anyone who helps me out

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Crisis on Infinite Earths runs for 12 issues, #'s 1-12.

The other books are indeed tie-in comics. Those serve to accentuate/extend elements of the main story. They’re fun, but in the case of most event stories they’re not 100% necessary to read.

I haven’t read all of the Crisis tie-ins, but at a glance, they appear to be in reading order here. I could be mistaken.