If you have used a Wainwright guide before, you won't need to be informed any further just how wonderful these pocket books are. However, if you are a newcomer to the fells, or haven't come across this series yet, then please believe me when I say that there is simply no better companion to exploring the peaks of the Lake District.
For those whose interest is purely to walk the fells, these books cover every angle of the mountains to a remarkable extent, including route descriptions, maps, summit views, and some beautiful hand-drawn pictures by the author. Be aware that these guides cover the fells only, though, so for a wider coverage regarding attractions, etc. within the Lake District, you will require another guidebook in addition. I know that for me, at least, these books are more than enough!
Wainwright's books were fastidious and personal account of his Lakeland, which makes them a thoroughly enjoyable read - all too often now, most guides just describe facts in an incredibly detached manner, and how to get the most for your money.
Though I have a great deal of affection for the original books, I would recommend the revised editions, updated by Chris Jesty, which are distinguished from the original editions by the colour photographs on the cover. Wainwright himself was more than aware that in the future his guides would become steadily inaccurate, since mountain paths come and go over 50 years, and Mr Jesty has done a diligent job in detailing changes that have occurred to the original routes and their environment, whilst maintaining the spirit of the original guides. In addition, the paths are marked in red ink on the maps, making them much easier to follow whilst on the fells.
Though the book of each area is, in my opinion, essential whilst walking in that region of the Lakes, I must make some comment regarding the specific details of this book, The North Western Fells. The fell density is a lot greater in this region than in most of the Lake District, and as such ascending the slopes can be more tiring due to the relative steepness. However, this is compensated for by some spectacular ridges joining the peaks, and I can quite happily spend a day up on the fells, crossing from summit to summit. For a quick and relatively painless walk, though, Catbells is a pretty little fell, and ideal for a family walking trip.
In short, if you are new to walking in an area of the fells, or merely want a new perspective, these books are essential!