"The Evangelical community has not been able to recoup what the Catholics and the Mainline Protestants have lost," he maintained.
Other chapters in the book explore the relationship between Evangelicals and various religions, with globalization bringing people of different faiths closer together geographically.
Stiller, who last week visited Venezuela in the midst of its economic crisis, said that he has had in-depth conversations with leaders in the Catholic Church, including with Pope Francis in 2014, and has mixed feelings about the prospects of the relationship between Evangelicals and Catholics improving in the near future.
"I met with the chair of the Venezuelan Bishops Conference, and we had a wonderful time of prayer, and discussing the current crisis in Venezuela," he said.
"I do know that there are some countries with Catholic majorities, where Evangelicals have been persecuted," he said, pointing to countries in Latin America and Italy, among others.
Stiller shared about his observations in Venezuela: "What I learned there is that there is an enormous move of God within the Evangelical Pentecostal world. It brought some push-back from the Catholic church at first, and some feel, really badly done by the Catholic church, but what I have seen is that the new kind of preaching has spilled over into the Catholic church, and brought renewal to its worship services and to the involvement of laity."
One major issue Pope Francis has been urging Christians to unite on has been in tackling climate change and environmental degradation. Stiller said that he feels Evangelicals should own this issue, and shared that God called on humans to co-manage His creation.
"That was the first assignment given to our parents. It is our mandate. We know [from] Scripture, the Earth is the Lord's, this is God's world. I think that is a position one can find resonance within the Evangelical community."
He suggested that the reason some Evangelicals have resisted the environmental movement is that it has often been driven by some with a more socialist, central government-management philosophy, which they feel uncomfortable with.
"The fact is we have polluted our rivers, we are emptying our oceans of its produce. I flew over sections of the Amazon on Friday, seeing huge patches of trees being cut down for fields. And the Amazon is the great set of lungs for the world," Stiller shared.
"Increasingly we are recognizing [that] this role of managing and caring for the environment in a prudent and balanced way is a call from Christ, and it is part of our mandate," he added.
"We cannot hide our heads in the sands. We are being willfully disobedient to the Lord if we allow His Creation to sink into desecration."
Returning to the topic of his trip to Venezuela, where Stiller had the opportunity to speak with both political and religious leaders and give the Minister of Religion there a copy of Evangelicals Around the World, the WEA Global Ambassador shared that in the midst of the crisis, he experienced something of great inspiration.
While in Caracas one night, where the crime rate is high and masses of people are lined up from early in the morning at the stores for food, suffering the consequences of what Stiller called a Marxist government that has bankrupted the country, he walked by a long line of protestors who started screaming and shouting at him, assuming he is an American and part of the problems that led to the financial collapse.
Further down the street, however, he encountered 2,000 Christians in deep prayer and worship at the Iglesia Evangelica Pentecostal in Las Acasia, the largest Evangelical church in the country, embodying a radically different attitude.
Stiller said that the contrast between the angry protestors and the prayerful Christians, though living in the same harsh conditions, provided a "stark reminder of the nature of the kingdom of Christ."
Evangelicals Around the World is available on Amazon.com.