I'm giving this 5 out of 5 to take into account the knock-down price of $4.99.
(Abridged review/thoughts from own blog http://bit.ly/rpgblog)
White Dwarf and Imagine (Uk's version of Dragon magazine) used to fill their pages with articles about time travel in D&D, Judge Dredd, CoC and, naturally, Star Trek. Grandfather paradoxes aplenty, time travel looked fun, but pretty unplayable.
Timemaster, however, does a good job of setting clear guidelines as to how to make Time travel work. You're Time Agents - fix the problems, apprehend the criminals, preserve the order. Time is a very mutable thing. Success and failure would be measured in terms of the "significance" of adventure goals on the rest of history (based on a points system). History had a way of healing itself, the trick was minimising the damage. For example, no matter what you did, the earth would be engulfed in a nuclear apocalypse at some point in late 20th to mid 21st Century, but the superpowers combatants may have actually changed in nationality. Maybe Hitler wins WWII and the Cold War is between just Europe and Russia, but eventually America is dragged into WWIII. The guidelines for this is pretty good. Even dropping a gun in the wrong time-period has a "Significance Rating". Any mistakes or failures are counted up against more general goals, making sure that a historical event actual takes place can outweigh the smaller problems. On top of that the rules include a comprehensive mass combat system with counters, which actually allow you to fight battles in history. Again, losing a battle, when in history it's actually won, may still not disrupt the time-line much. A war may drag on for a few more months with the same overall result. Alternatively there could be catastrophe with the time-line not getting back on track for 500 years. Then you have to think "Well, the whole 16th-21st Century were ruined, as long as Earth still joins the Interstellar Community in the 24th Century, the Time Corp HQ in the 72nd century won't actually get wiped out". Dominoes.
There is an open feel and yet a totality about the rules in Timemaster. It's limitations seem to depend upon your own perceptions of sci-fi and science. For example PCs are enlisted from any point in history, but are discouraged from entering their own time - which closes quite a few interesting doors. Also, the rules for futuristic weapons seem to be limited to Space-fighters, a laser gun and laser rifle. Hmm. There's a lot of time between here and the 72nd century. Creativity is required on behalf of the Referee in terms of small details. The emphasis is often on famous people or royals from history plus an unwanted element - a "Demorean" (multiple armed xenophobic perfectist interdimensional aliens) or just some time-travel-renegade, a mercenary from the "Time-Wars".
From the handful of scenarios I've seen, the basic plot is:
Historically important NPCs
(approaching a) Major Historical Event
(acquire) influence/help/anachronistic weapon *
(from) bad guy(s)...
... the PCs (must) confiscate the item
(and) destroy or arrest the bad guys,
(whilst) preserving life and time-line event order.
*(the Spanish Armada have a Polaris missile in Sea Dogs of England)
The problem is that it can all read like a pantomime comedy in period costume. Did I mention that despite the extra limbs, that bad-guy-evil Demoreans can shape-shift? Masquerading as our leaders!? The Horror!
When I was younger I struggled a lot with the sweeping generalisations about history in Timemaster which seemed at odds with fairly detailed battlefield simulations. I was utterly tied in knots about actually getting down to play Timemaster.
However, since the TV series Doctor Who went utterly crazy, I'm feeling less worried about Churchill punching out aliens and lasers at the Somme. And yes, you could probably do the "spitfires in space" thing but the debriefing back at the Time Corps would be really tough.
Oh, and another thing - the Chronoscooters can only jump in and then jump back to HQ 72ndC. from one time - no "time-hopping". In one of the modules they throw that out of the window on the second page. What's the point of time-travel if one mission doesn't involve several different time periods in rapid succession? Maybe I'd have been better off meddling in the "Time Wars".
In summary, the main rules are an excellent stepping off point into to time travel gaming, but it needs just a little more "tech" (it was lacking in the 80s), and a confident, flexible DM would probably have the most fun playing everything as the "exception to rule".
The art in the main rules is less than inspiring - mainly Victorian wood-cuts - with a little more cut and paste Terry Gilliam would have had a run for his money. But it's still adorable as a complete old-style numbers and bonuses role-playing system.
Overall it's a very comprehensive and complete system, the setting will appeal to both serious players, and Time Bandits fans. ;)
Billiam B (Adventures and Shopping http://bit.ly/rpgblog )
[5 of 5 Stars!]