A solo ad is a one time email blast you buy from a vendor that has created a "list" of people they have collected. Should it be part of your marketing campaign? Sure, why not? For as little as $10 it is worth a shot to see if you get a reaction from email on your product.
Is email marketing effective? Once you buy the Solo ad, step back and carefully analyze what just happened. You may not have tweak anything if it worked well. If it doesn't work for you, it may need tweaked or it may not be suitable for your product.