if you want to go the old school struggle route, that is up to you -- but i recommend you do the free trial subscription at www.hamtestonline.com to see how easy this program will make getting your Extra
the software presents the study material to you (no other books or resources needed) and continually tests you with actual FCC exam questions, and then over-trains you in your weak areas based on the the exam questions & areas you are not passing. it also let's you know when you are ready to pass with flying colors.
after trying it out for free, you will want to pay for a subscription so you have access to the full training material for the exam. keep in mind you wont need to purchase any other materials to study from and you will *know* when you are ready to pass.
if you have any doubts, check out the eham reviews of it at https://www.eham.net/reviews/detail/3412
when 768 hams all agree and give something 5 out of 5 stars -- you darn well know it is especially good 
This.
i decided in January I wanted to get my ham license (thought about it in 1974, but both the code test and the electronics on the written test were an issue). Took a practice exam online for Technician, passed cold (I've learned some electronics in the past 45 years, and no code test any more). Decided to get General, found hamtestonline.com, bought the General course after trying to free trial, got to "passing" in
one week. Had three weeks still to go before my testing date, decided to try Extra too. Bought that course (due to a special on General when I signed up, I now had $60 into this). A week before the test date, I had easily reached "passing" on Extra as well. Kept drilling, and by testing date, there were only two or three questions combined in the General and Extra pools that I had trouble with.
When I took the exams, I went through Technician, General, and Extra in an hour and a half. I missed two questions on Tech (which I hadn't studied at all, though the material for General and Extra apparently transferred some), one on General, and one on Extra -- after four or five weeks of no more than an hour of study a day, in a format that was more like an online trivia quiz with answers provided.
Now, I take multiple choice tests well, always have (since the 1960s), but in studying for these I found I knew a lot more about electronics than I thought I had, hidden knowledge that the study material built on to give me the confidence for questions about transistor circuits, FETs, and voltage regulators. I learned enough about antennae to not feel I'd just memorized those answers -- and I (temporarily) memorized enough regulations and band allocation information to pass the test (this is all stuff you'd always look up in real life anyway, and much of what isn't "just sensible" is fine points and edge cases anyway). I had an advantage in being able to do all the arithmetic in my head -- but the formulae came from the study materials, and knowing those, anyone who remembers the most basic of trigonometry (what's the sin of 30 degrees?) can do the necessary calculations with their testing pencil on the scratch sheet provided.
Bottom line: unless you're a Luddite, or can't afford the cost of the course (and if you can't, it's going to be a long, slow slog trying to build a station), hamtestonline.com is the best money you'll ever spend in ham radio.