Simmons' addition to the canon is an interesting read, for the most part. His version of Sherlock Holmes is pitch perfect, as the detective joins forces with Henry James to solve a mystery in the U.S., while pondering the reality of his own existence. The historical figures that the pair encounter, fictional ones included, are all well represented. Although Simmons is rapidly becoming the Tom Clancy of historical research, which does bog down the pacing, at least his output is more readable than Clancy's skeins of schematic scribbling.
In the final accounting, an enjoyable read for fans of both Holmes and Simmons.