I am a new believer and struggling to find a good church. Many of the churches close to me are big enough to have gift shops inside! Isn't this wrong? Selling next to where they are preaching doesn't seem right to me. Didn't Jesus say not to turn his father's house into a market?
Jesus' comment regarding selling in the temple of God was made in a specific context:
Jesus' disgust at the activities in the temple reflect the specific nature of the temple and of these offenses. The temple was intended as a meeting place for God and men, but over the centuries the Pharisees turned it into a place of commerce. The danger in this practice was in diminishing the importance of God and the purpose of the temple.
In our day, the temple of God is the physical body of the believer:
So the direct application of Jesus' concerns in Mark 11 would be that we work to purify our body from unholy behavior. This is our spiritual service of worship Paul says:
Therefore, the church building we attend is not the temple of God. It's just a building, and as such it has no significance on its own. So we cannot take Jesus' words regarding the Jewish temple and apply them to a different kind of building, in this case a church.
Nevertheless, the New Testament does give rules for how the assembly of God's people should take place in any space:
Paul admonished the church in Corinth to meet in an orderly, loving fashion without resorting to selfish debauchery. Therefore, anything done in the context of the gathering which detracts from order and godliness would be wrong. Is selling books in the church building contrary to these requirements? Not necessarily, and in the end that would be a judgment call for the elders to make.