So my wife (36F) and I (34M) have been together 19 years and married 15 years we have grade schools kids. We have a good relationship don't fight often, communicate pretty well, sex 2-3 times a week, enjoy spending time together etc. I feel like we have gotten a little "stale" in the past 6-8 months again I/we are not unhappy or in a bad place just feeling a little routine and mundane. I am looking for some type of book for couples that we can rejuvenate our marriage would prefer not Christian based. We've read 5 love languages and liked it. A workbook almost daily devotional type of book would be ideal. All the books I have googled seem to be for relationships that are having issues or are on the rocks. I don't feel like we need that.

TL:DR Books/workbook style book for marriage not having problems just looking to rejuvenate and improve an already strong relationship.