I've blogged about The Entertainer before, its a handy little 2 for 1 (mostly but not exclusively) voucher book which is now also available as an app for your phone. Some of these vouchers are really useful and can be a great way to get out and about in Muscat to try out new activities or restaurants that you may not have otherwise tried out.
Back in the day when this thing was just a book (and not the app) I found I was constantly leaving the thing at home and thus not making the most use out of it, but since the app came out, seeing as we all seem to be surgically attached to our phones, I don't have this problem anymore. You can even transfer your e-vouchers to your friends if you don't use them
Anywho, they are currently offering an early bird special for 2017 for RO 20 (instead of RO 25) which if you purchase before the end of this month you also get 2016 vouchers activated (in the phone app) for free,
Not a bad deal!