Yes, Dave from PublisherRocket. I have PR and it's a great tool. I respect Dave's opinion, but the most important thing I've learned from running ads is to always test for yourself and see how it works. What works for one author might not work for the next and visa versa. I switched to targeting categories because it got to where some of my keyword ads weren't getting impressions. It didn't matter how much I bid or how high my budget was, impressions just wouldn't happen. Some ads would get tons of impressions and some wouldn't budge despite all being in the same genres and targeting the same audiences. It was so frustrating. It's like Amazon didn't want my money!
I knew I had to switch things up. I had tried product ads before and didn't like them. It seems impossible getting impressions and I haven't heard anyone saying they have luck with product ads. Cat ads get tons of impressions quickly and they are much cheaper than targeting keywords. For example, I had four cat ads running with a daily budget of 25.00 each and I average at least 20,000 or more impressions a day on each of them and the most I've spent in one day was 14.00 for all FOUR. If I was running keyword ads and getting that many impressions I'd have to bid more than I do with cat ads and would probably be spending 100 dollars or more with a 25 dollar budget each for four ads. No way.
Normally, I wouldn't dare bid 25 dollars a day for 4 ads but I can do it with cat ads because I know there is no way the money will be spent in a day for any of them. Three of them rarely spend a dollar yet I get tons of impressions and a good amount of clicks and sales. The other is for my new release and it spends the most each day but it's no more than 5 dollars usually. One day it spent 9. I budgeted 25 dollars just so Amazon kept the ads running. I've since lowered my budget of those ads because I tested and saw I still got many impressions and the ads don't run out with lesser budgets. With keyword ads, I spend my budget every single day.
With cat ads you can bid very cheap and still get tons of impressions. Most of the bid suggestions for cat ads don't go past .30 cents. Many are much cheaper than that depending on the category. With the bids I am doing, the highest I am bidding is .33 a click and I spend about .20 cents though. The rest are 20 cents and below which means I am spending less than .20. Many cats have such low bids you'll be paying 4 cents a click and still get impressions.
The key though is to pick the best cat for your work and then try to narrow it down if possible to a tighter cat. It's not always possible though so sometimes you gotta stick with the general category or be creative with cats.
Another thing, most authors don't target cats so that's why the bids are so cheap. Most authors do the regular keyword ads and you don't hear much about cat ads so I'm not sure many even know about them.
So yes, try everything and you can even try product targeting just to see how they work for you. When targeting products you don't have to stick to books. You can target MOVIES in your genre too. If you know the name of a movie, type it in like a book title and see if it comes up or look it up on Amazon and put the ASIN in the search box like a book.
Another important thing is negative targeting. Many authors ignore this but it's important to use. When doing categories or products you can actually put the ASIN or names of books that you don't want your book advertised with. For example if you write romantic suspense but don't want your book showing up with the cozies, you can put the ASIN of some popular cozy mystery authors or some in the Top 100 and exclude them from your targeting. With keywords, just put in keywords that you want to be avoided when people search for your book. Negative targeting saves you money in the end.
The cool thing about category targeting is that the product page of books your book is advertised on will come up on the search terms page on your dashboard. You'll be able to see every book page you show up on and then you can see if the books fit yours and exclude any if need be.
A lot goes into it and after using AMS for about four years I am still learning. LOL!
Hope I helped!