Is there a cap to how many readers can participate in my ARC?
No. You can invite as many readers as you like to join your ARC on BookSirens.
You can also set a cap for how many readers can download your ARC. This is useful if, for example, you want to send the invitation to 500 readers on your mailing list but only want to offer 25 available spots on a first-come-first-serve basis.
You can set the cap on a book by book basis via your book's dashboard.
You can change these limits at any time.