The 1:25000 scale is great as it replicates the UK Ordnance Survey Explorer scale of mapping but the resemblance pretty much stops there.
In typical Manx fashion they do look different to OS or Harvey's Maps and do take a little getting used to e.g. RoW footpaths/Greenways etc are identified different to the OS or Harvey maps and there are the odd inaccuracies (for example some of the Triangulation Pillars are shown in typical OS form whilst others are ignored completely).
If you want a 1:25000 map of the island you have no choice other than these. Available on the internet and widely across the island and cheap compared to OS maps, the whole island 1:25000 paper mapping would cost you (at least) twice as much if it was an OS version.
The downside is the quality of the paper the maps are printed on. It's very thin (compared to OS or Harveys) and over 15+ years on holidaying on the island (2-4 weeks per year) I've found I've needed to replace them every other year as they start to fall apart at the folds. The plastic sleeve they come in is ok to protect a folded map but not much use if you're out on the moor viewing the open map in the rain.
Sadly, I'm not aware that anywhere sells a laminated version of the 1:25000 map.
A good scale map on two double sided sheets. Having to swap over sides is restrictive when on the bike. But the alternative is smaller scale i.e the OS Landranger series or having four sheets. Two double sided sheets is a good compromise.
If you think this will be the definitive for trail riding think again! Some of the Greenaways are easily passable and some of the 'Public Roads, with restrictions' are almost impassable. This map will guide you, but normal trail cautions should be exercised. There are significant 'dark' areas on the IOM with no cellphone coverage.