Solid three-part adventure showcasing the Eric Roberts version of The Master.
I hadn't been too impressed with Eric Roberts' previous few appearances in Big Finish releases. "The Lifeboat and the Deathboat" (from The Diary of River Song) was very meh. And in Masterful and the finale of "Ravenous" he was sharing the spotlight with other incarnations of the Master. So I wasn't sure how he was going to be in his first "starring role." Master! puts the focus on him and really gives him an opportunity to show us what this incarnation of the Master can be. And just like each incarnation of The Doctor is different, so is each incarnation of The Master. Roberts' Master comes off like a calculating corporate CEO and/or crime boss rather than a lunatic with crazy, universe-conquering (or destroying) plans. Perhaps it's because he's the only American to play the role, but I think this persona works well for him, and should provide the template for future appearances. And I hope there are plenty of future appearances.
Though Vienna doesn't show up until Part 2, this feels very much like Vienna, Series 5. (And I hope we do eventually get a Vienna, Series 5, but this will be the placeholder for now.) Sidekick Jexie is name-checked (placing this somewhere post-Series 2), though she doesn't appear. Rather, Vienna is paired with a robot she nicknames Artie. It works, and gives her someone to talk to during the action, but this is Vienna, on her own, doing one last bounty-hunting job against Jexie's advice. And Chase Masterson once again nails the cheerfully cynical role. (In the "behind the scenes" portion she refers to Vienna as a combination of La Femme Nikita and Elaine from Seinfeld. My goodness, what a comparison.)
While Vienna is technically a spinoff of Doctor Who, this is the first time since her intial appearance in The Shadow Heart where the Whoniverse has even been referenced. As with Counter-Measures, I don't think Vienna needs "stunt casting" from the parent series, but if that's what it takes to boost sales of her own series and make a Vienna, Series 5 (and 6 and 7) more likely, then go ahead, and have her encountering The Master and Daleks.
Daleks. Yeah, I was rather skeptical that Daleks were going to be shoved into this release. But there's a very in-universe reason for them to be here, and it works. Nor do they dominate the narrative. Also, who knew there was such a thing as a Dalek Litigator. BF has given us many different kinds of Daleks, but a Lawyer-Dalek was amusingly unexpected.
To sum up -- it's the sort of solid, fun adventure one expects from a Vienna, release, and Eric Roberts absolutely owns the role of The Master. At last.