Etherscope is an excellent value D20 system role playing game set in an alternate earth where the British Empire never fell and alternate technology (steampunkish) reigns.
It is, however, a science *fantasy* background rather than a science *fiction* one ... which you should have expected anyway! So be warned.
That said, the elements of fantasy science are consistent and well thought out and set the scene well and there is an extensive amount of information provided on all aspects, including extensive equipment lists.
The character classes are quite generic but this is not a problem as the designers have included a system of careers (Templates) that will enhance the individuality of each character despite this.
The only quibble I have, as a professional historian, is the history and its interpretation ... not the alternative history so much, but the interpretation of history *before* the point of divergence. To say that it was a unique interpretation would be close ... but it would be more accurate to say that, at best, it is totally misleading and, at worst, downright *wrong* ... but that's a quibble. Most players won't know enough to notice ... and, if the GMs do, they'll just ignore the sillier parts as I will.
All in all this book is excellent value for money (the production values are outstanding!) and I highly recommend it for a group wanting something genuinely different, the one quibble aside.