Whilst not bad for the price (I got my copy for $11) SPQR has the look of a somewhat unpolished product.
I've read through several times now and still do not really understand the order system or how it works - as the core of the system this should be made very clear but there is not so much as an example of issuing orders and what effect that would have on play, the orders section really needs expanding and several examples adding.
The interaction between general and other officers is also unclear - how do officers use their points and how does it differ from the generals command pips?
The combat section is clear, and has some unusual mechanics (including charges being initially treated as ranged combat) which I have yet to try on the table.
Several army lists and scenarios are included and this part of the book seems well done and thought out.
It's worth noting that there is a very active yahoo group which covers these rules too.
In summary, if you are willing to put the work in on the yahoo group getting the rest of the rules down (they don't appear to be in the book) then this might be a good set of rules.