I haven't read the book but I wanted to comment on what Andrew had to say, my reply was too lengthy (oops!) so I've included it here and linked to it in Andrew's comments section.
I realize I'm a little late to reply to this post, but I'm going to anyway.
The seeming 'tension' between the Evangelical church and the workplace is quite an odd one - and let me flesh out what I mean by tension.
It is right that there is a big push for evangelical Christians to enter into full-time Christian ministry - there is a lack of able, teaching Christian men and women entering this 'field' (for lack of a better term) but I can't help but feel that the big push of this actually undermines the importance of the Christian in the workplace.
Christian ministry is something that requires the 'employee' to both have a desire to work in this field and the support from their local church (meaning their pastors and teachers) to do so. So is it right to so publicly urge people to enter Christian ministry? (I'm thinking at the front of conferences, visiting missionaries etc.)
I've been working at a company in Liverpool for just over 2 years now and it is almost a constant battle between two inner lines of thought - one that says that my work is worthwhile because of the friends I make at work (who I then am trying to introduce the Lord Jesus to) and the influence that I hold in a local business - urging them to avoid illegal practice, reminding them that work is not my reason to live and therefore I am not available to sleep in the office all the time. (Some colleagues until recently hadn't had a day off for 4 months!)
However, the other inner thought is that my work isn't worth while and I find myself considering leaving this work behind to become a missionary or other full time ministry role. Part of me can't help but feel this is a more holy pursuit.
This is when I arrive at my final position that there is no reason why I cannot hold these two things together.
I am a missionary - in my workplace! I also feel that whilst being able to work where I do (admittedly taking part in work that I actually love - not just merely think is acceptable - I have been blessed!) I can still exercise my gifts in the local church and (here comes the best part) then share with my friends at work how that is going.
For example, it has often been a great thing to be able to share with colleagues that I'm preaching at the weekend - they'll sometimes ask what I'm preaching on, what does it mean, how do I know what it means, how does it apply to us in today's world etc. I don't think I'm particularly blessed with 'thinking' friends but that it is merely a matter of sharing our lives with them! In fact, as I wrote this on the train to work, a colleague who I travel to work with asked me what am I writing and consequently what an 'Evangelical' Christian is!
Before working where I do, I worked as a ministry trainee at Christ Church Liverpool (as you know, Andrew) and when I left there to work at my current employment I asked a friend of mine what should I do in future? How long should I work in secular employment? Should I return to full-time Christian ministry at some point?
His answer was that I am capable of earning a lot of money to fund Christian ministry and should therefore do so.
This was initially enough of an answer for me and actually fueled my progression at work to be able to earn more money but as time has progressed I've realised that my time spent with friends is far more valuable to me than the by-product of earning money to fund holier employment.
I want to comment on the subject of profit that Grudem discusses - but I feel I have nothing to add. Apart from what does Grudem mean but it being a help to the person he has had a transaction with?
My first stab at an answer would be that the church should most definately encourage their congregations to take part in business - and indeed in transactions that involve making profit.
The reason I would say so is that it is good to take part in all areas of life and to show an example of how to fairly 'do' business and to not act for dishonest gain.
Of course, not all Christians should take part in business as perhaps their hearts cannot cope - the temptation of dishonest gain may be too much - but we cannot falter as a church at that hurdle and frown upon business and profit, as that is the issue with every worldly pursuit, that we are all sinful, selfish, idolatrous, hard hearted people.