When I think of the book of Isaiah, I have to admit that I think of what I would call "scriptural elitists," who claim it is their favorite book of scripture.
Well, so far, I either haven't taken the time or had the intellectually energy to approach the table and see if I could sit with the scriptural Lao Tzus, Gandhis, or Dumbledores. I'm just not there yet.
That being said, before I ever get the chance to dig in to Isaiah, here are some things that I've read are helpful:
1. Study the historic and religious context. Isaiah spoke to the Jews about things they were familiar with and understood. If you are 2500+ yr-old Jew, you got this. If not, perhaps you should do some poking around and see what you can find about what was happening back then. The church has some great resources in the scriptures and on lds.org. Check it out. But only if you want to understand.
2. Have the "spirit of prophecy," as mentioned in 2 Nephi 25:4. If you are just reading to check the box, you're not gonna get it. You need to be studying and prayerfully considering what you are studying...but only if you want to understand.
3. Remember that Isaiah used a lot of dualism in his prophecies. He prophesied of then-current events that also were prophecies of future events. Kind of like a very efficient "2 birds with one stone." This can make it easy to miss the relevant prophecies of our day, because it looks like he's going on about things that already happened forever ago. See #2.
The Bible Dictionary tells us that Isaiah teaches of the coming of the Messiah, the gathering of the house of Israel, the cleansing of the earth, and many other prophecies that both have and have not already occurred. It is up to you, the reader, to sort it all out.
But not without help.