In addition to the 'Milepost' there are two other publications recommended - Mike and Terri Church's 'Alaskan Camping' which includes Canada and the Yukon. It's all you will need for finding RV parks, public campgrounds and awesome boondocking spots near the highways. Also purchase the TourSaver 2/1 Coupon Book available online. One glacier cruise will pay for the book and you'll want to do at least one.
As stated above the highway is good for the most part but just like the lower 48, there will be construction during the summer months. Just go with the flow.
Many things are far apart so plan to stop and sitesee along the way. Don't think you'll get to the campground and then backtrack to see something.
A whole summer of reservations is not needed. The only ones we made were for the July 4 weekend (Alaskans like to camp, too), and for 5 night's in Denali's farthest campground you can drive - Teklanika. For those we only made them about 3 weeks prior when we could better judge where and when we'd be there. As it turned out we were early getting into the Denali area so on a whim we boondocked at a lovely spot nearby the previous night and drove into the park early morning. We easily secured without reservations an additional 5 nights in Riley Creek campground for our 40' motorhome. Spending 10 nights in Denali we saw 'THE' mountain 7 of 10 days (some never see it) and saw every one of the big five animals residing in the park - more than once.
There are really no 'resort' RV parks as you may see in the lower 48. Most RV parks are just gravel parking lots so you don't have to pay big bucks for a place to stay.
Definitely plan on exploring Canada and the Yukon on your way to Alaska. They are beautiful countries.
Read as much as you can on these forums. During the winter months there will be lots of postings. Woodalls.com forum also has a good ongoing Alaska posting of those planning to go the summer of 2017. Folks even post on it as they're traveling to alert for road conditions or other issues. The 2016 post is going on right now if you want to check it out.
Every year is different for road conditions and don't listen to the horror stories of years past.
Plan to take as much time as you can. Most leave the last part of May and return the end of August. It's not a trip you'll want to rush through.
Have fun planning!