Frankly, anything explicitly marketed to American conservatives these days is mostly ragebait for stupid people and I doubt you'll find any of it the least bit convincing. As other have mentioned, Thomas Sowell is a great place to start if you want something serious but modern and clearly written. Milton Friedman's Free to Choose or Capitalism and Freedom are both widely recommended classics. If you managed to read Marx without dying of boredom you should also be able to get through Ludwig von Mises' Human Action or Socialism.