Are Porcelain Veneers Recommended for Really Crooked Teeth?

The short answer is that veneers CAN be put on really crooked teeth but a lot of times this INCREASES the amount of tooth reduction that is necessary.   When teeth are overlapping or flaring it's pretty much impossible to get a good result with veneers without doing some serious modification of your teeth.   If your teeth are really crooked I would recommend doing an accelerated Invisalign movement to at least get you closer to being straight.  Doing veneers on teeth that are 'generally' in the right position increases the esthetic outcome.  They look more natural, the gumline is more precise, they have uniform thickness (or thin-ness).  

If they are extremely crooked, it is best to have them aligned first either with braces or Invisalign. That way if veneers are placed after you will have much better aesthetic results, and you will be able to have more conservative preparations of your teeth, which will be better for you. If they are only slightly crooked then it's possible to proceed with the veneers without orthodontics, but it sounds like in your case orthodontics prior to veneer placement is advised.