Welcome to FileMaker Pro.
I have met a number of experienced developers moving to FileMaker Pro in the past. They have a tendency to fall into one of two positions after moving to FileMaker Pro. Either they love or hate FileMaker Pro.
I have noticed that those who hate it complain a lot about performance and feature set. They often talk about how SQL can perform faster or how PHP has so many more features or how the layout engine has so many restrictions compared to HTML. They also seem to forget they came from three separate environments (SQL, PHP and HTML) that each have their own optimization rules to FileMaker Pro, an integrated environment that also has its optimization rules.
I have noticed that those who love FileMaker Pro often talk about how easy it is to administer FileMaker Server, especially in regards to backing up. I have also heard them talk about how it is so nice not to worry about record locking, how making a UI is simpler, how there is not a ton of settings to set for controls (although with all the new features being added, we are getting close to a ton of settings), etc.
Access and FileMaker are different beasts. For one, you can not swap FileMaker Pro's database engine. For two, FileMaker Pro's database is not remotely close to a SQL database. For three, FileMaker Pro is targeted to novice users, even if it has many powerful features. There is no Visual Basic or macros, just FileMaker Pro's scripting engine. The security model is much more robust. You can view a side by side comparison between the two here.
Unfortunately, there is no book I am aware of written for the true programmer about FileMaker Pro. There are WEB sites that have free templates that could point you in the right direction (start here). FileMaker also sells the FileMaker Training Series manual, a great place to start. FileMaker Magazine publishes many videos of tips and tricks that are helpful to developers of all skill levels.
No matter what, be aware that making truly advanced FileMaker solution will require experience. The resources mentioned above can only speed up that process.