Which Book Promotion Services Are Worth It?

Has anyone tried professional book promotion services recently? I’m curious about which services actually help increase book sales and visibility without overspending. Are some platforms or strategies more effective than others for reaching target readers? How do you measure the success of a promotion campaign, and are there hidden fees authors should watch out for? I’d love to hear your experiences, tips, or recommendations for reliable book promotion services that deliver real results and help your book stand out.