I bought Romanov Prophecy a few years ago. You're right; it is a good book. Some have knocked Steve for his writing style, but personally I rather like it. The last few chapters of RP in particular are amazing, with (I'm going to use spoiler tags here just in case)
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Lord, Akilina, and Michael's confrontation with the villians, Alexei the dog sacrificing himself to take Taylor Hayes down, and Thorn's coronation as Michael II. I do wish, though, that the book had mentioned Thorn's patronymic so we would have known his father's name.
I've also read The Third Secret and The Columbus Affair. TS is rather forgettable, but CA is very good.
Have you read any of Berry's Cotton Malone series? I tried to read Templar Legacy a few years ago but couldn't really get into it. I'm thinking about giving the series another go, though, because his two recent works, The Tudor Plot and The King's Deception both deal with English history, which I'm a sucker for.