You can probably figure it out without a definition, but a read-alike is a book or series that shares a commonality with another book or series that might appeal to the same reader. It could be a similar tone, setting, depth of characterization or type of plot. A good read-alike connects the elements you enjoy through different books and authors.
I was encouraged to read the first two books in a new Scottish series by Maya Banks over the weekend because I read somewhere that this series shared settings and tone and types of characters with the Scottish historical series Julie Garwood wrote in the 1980s and 90s. This was a really good recommendation, as I could see the similarities and the differences and I enjoyed them both. (By the way, I love the new publishing trend of releasing books in trilogies one month apart so the wait isn't so bad.)
So, may I suggest one of the read-alikes listed below or is there anyone out there who has their own romance read-alike to share?