(3) Base Camp
Fear not, intrepid reader. Isaac Asimov's Foundation is like a light hike through the forest. Asimov paves his sentences to offer a helping hand to all levels of readers. His characters make sure you'll never lose the path. In fact, the hardest part of reading Foundation is finding the strength to set the novel aside before you finish.
Now, this isn't to say that Foundation isn't worth your time, because it is. You just won't need a camp stove and a 4-day supply of beef jerky to take in the views—just a walking stick and a water bottle.