Ships from and sold by Amazon.com. I am a huge Minecraft fan, and I think this book has all of the knowledge you would ever need to negotiate the strange terrain of the Nether and the End, as well as battle the local... Survival is difficult in the perilous Nether and End dimensions, and you'll need to up your game if you want to make it back to the Overworld.
The starting points are predetermined by your map seed. Nether Fortress Finder does this the same way Minecraft does, so it's safe to use letters (and other characters) as well. Minecraft Nether update new biomes.