If there has been an offer of a circulating ARC of Horizon for North American listees, I missed it. James Bryant has one making the rounds for those not in N.A.
I have obtained a Horizon ARC that I'm willing to let circulate, and will borrow from James's statement of conditions for those who are interested in reading it:
 You will buy your own copy when the book is published,
 You will report receipt by email to me and the rest of the recipient list and forward it, within no more than three days of receiving it, to the next person on the list, This gives you
two full days to read it. If there's more than one person in the house who wants to read it, you can have one more day.
 You will pass it on by hand if you live within a reasonable distance of the next recipient, or will forward it at your own expense using FedEx or any other service which offers on-line tracking, and will email the tracking number to me and everyone on the list of recipients so any of us can watch its progress, and
 You will take good care of the book while it is in your possession.
I'll take names of people interested until Monday, November 10, and then will organize the list of recipients and get it on the way. Send your request with your mailing address to me OFF LIST, please.