Ditto on 2gypsies comments!
Suggest buying all three books they recommend as they will pay for themselves quickly. If you purchase The Milepost and Mike and Terri Church's 'Alaskan Camping' you will need no other reference material!
We made advanced reservations on holiday weekends and at major attractions while in Alaska. Otherwise we would check our references while on the road sometime during the morning and call ahead for a reservation for that evening, once we knew what time we wanted to stop driving while in Alaska. Since phone service was expensive for us in Canada we made no reservations there except at Toad River. (We want a spot on the lake and they fill up quickly.)
We do fair amount of boondocking as we like to not be surrounded by other folks and you can't bet the price.
It may be a bit more crowded this year as people shouldn't have to contend with $6.00 a gallon diesel fuel, as we did in the Yukon in 2014, but I would say go into it knowing this will be the trip of a lifetime!