I'm grateful to the publisher for giving me access to an advance e-copy of Beyond the Light Horizon to consider for review.

In a complex and satisfying conclusion to Macleod's Lightspeed trilogy, we see the consequences for Earth politics and development of the discovery of faster-than-light travel, and of planets inhabited by other species, become clear.

On a near future Earth, there are three main powers: the Union, a post-revolutionary society run as an "economic democracy" which has originated from the European Union, the Alliance, comprising much of the anglo world, and the Co-ord, bringing together authoritarian Russia and China. The focus is on the Union, which has just caught up with the (secret) FTL capability of the other two powers, and especially on John Grant, a somewhat restless and buccaneering member of the Revolutionary class known as the responsables. It was Grant who sponsored the creation of the Union's first FTL craft, opening a bewildering array of opportunities which he's determined to exploit.

Many of the possibilities flowing from that raise challenging ethical questions - I nearly typed "new" before that, but actually they're not - about the impact of settlement and colonisation on indigenous populations. The flora and fauna in the new planets being explored are so different that the humans are slow - perhaps deliberately slow - in identifying sentient life. They need a lot of help from Iskander, the AI that enables society in the Union, to do this and Iskander's role is, to my mind, somewhat ambiguous here. At least one player, Marcus Owen, the English robot agent, regards it as dangerous to humanity. Equally ambiguous is the alien race known as the Fermi. It may be planning to defend life on, for example, Apis but in the meantime a great deal of damage is being done.

I found it - what's the work - bracing? salutary? - how deftly Macleod portrays realistic outcomes from this situation. The Union is not, for example, a society of self-denying socialist co-operators, at least not until Iskander channels and directs their activity, so there is a very enthusiastic response to the call for colonisers and pioneers without a great deal of thought as to the consequences. Grant and his circle react in a similar way, at one stage proposing a somewhat hare-brained plan to introduce a sort of whaling industry on an untouched world.

Equally impressive is the sheer breadth of imagination shown here in the range of life and of planets supporting it, which all have complex and vibrant histories. Wise societies, some of them, which have accepted natural limits to expansion: restless ones, others, which want to press on and outwards. There is perhaps a bit of s sense of a whistlestop tour at times, because with so much in the background to this trilogy there isn't time to visit most of it. Characters and vessels come and go, trading patterns emerge rapidly and some of the individuals we have been following through the three books are perhaps slightly overshadowed by the pace and scale of events. That is, I think, inevitable and Macleod still manages to give everyone a satisfying resolution, aided in one or two cases by the judicious use of temporal paradoxes (although I lost sight of Owen in the end and couldn't help thinking he was off somewhere engaged in mischief).

Macleod's writing is always engaging, whether it's dropping references to other classic SF with similar themes, such as to 'intellects vast and cool and unsympathetic', to wider SF (a 'hero of the Revolution' who rather decries her public image as 'Red Sonia of [the] Rising', a mention of 'Union Space Marines') or nodding to the agenda of a left-wing meeting with its essential 'any other competent business'. The latter illustrates a distinct point about these books - their mental furniture steers clear of assumptions of a wholly capitalist future (without though adopting the Utopianism of Start Trek). The Lightspeed trilogy is rooted in a very different and distinct conception of future history, making the outworking of the story especially interesting and valuable to me.

All in all, a fitting end to this trilogy which has challenged, intrigued and instructed. Great fun, and never less than though provoking.

The biggest question about the final book in a trilogy is, will it stick the landing? So when you get three quarters of the way through the book and have to double check if it actually is a trilogy, well that could be problem. Luckily MacLeod does a magic trick in his last fifty pages and allows his audience to be content with a kind of ending to certain narrative plot points, whilst suggesting that the characters will go on to live long, complex lives - which is a real-life ending. And certainly one I didn't expect when I read the "Story So Far" recap at the beginning of the book, which horrified me with how much I had forgotten. My review of Beyond The Reach Of Earth (Book 2) mentioned how many balls had been tossed in the air by the first book, and that it didn't necessarily follow through with those whilst throwing a whole bunch more in the air. Beyond The Light Horizon is interesting in that we start with a whole new complex planetary system being discovered, more balls perhaps?

Despite this, and obviously with a nod to the previous world-building and character work, Feyond The Light Horizon is remarkably self-contained. We have a chapter to sort out the previous cliffhanger (two time loops are closed and then we don't worry so much about time travel again), and then the new system is discovered. One with three distinct forms of sentient species, a big marsupial race, some dinosaurs (and yes, this just calls them dinosaurs), and some humans stranded there in the past. Light touch world-building sets this up as appropriate to the universe (how they have interacted themselves with the Fermi), and then we get on with the usual political shenanigans that come with MacLeod's three-faction future Earth. He even gets to do a proper mystery reveal. and time his hints such that I think I got the solution about three pages before it actually unfolded.

I would be interested to revisit this as a trilogy to be read in one piece, where I think the lows of book two (how much the narrative sprawls) would not be a problem. That might also show a weakness however in how focussed book three is on a new location, Apis does get a bit of a look in, but not much. The solution to the "ancient intelligence that is meddling in all intelligent life" may seem a little underwhelming to start off with, but actual works better than a lot of similar antagonists, and has never had the sense that humanity faces destruction. Instead MacLeod gets to be a Utopianist here, even without solving factions and war on Earth, and bringing in a really rather sweetly banal first contact scenario. A win for socialist economics!