If there was one book any Christian could have, in addition to the Bible obvs, various candidates would be advanced. Historically, it would have been, in English speaking countries anyway, John Bunyan's "Pilgrims Progress". Other books might spring to mind. For me, JC Ryle's "Holiness" would be a strong challenger. Ryle was the (Victorian era) first ever Bishop of Liverpool and so in places the books are a little dated. Not many of us have to wrestle with issues around servants, for example! One or two other Victorian shibboleths like temperance also feature occasionally. The picture of Ryle looks just like a Victorian prophet but surely in 2015 he is hardly relevant to a world of Google and I-Pads? Just why is it that his books and especially his master work "Holiness" are so gripping? His books are certainly very distinctive in style. They have short sentences. They never pull punches. They are personal. They are powerful, challenging, meaty, rich in content and especially very strong on practical application. Many evangelical sermons and books we have today tend to be first rate in their theology but can on occasion fall short in their application of that theology to the everyday life of the reader. Not Ryle. Application is tough because its really the preacher or reader coming down out of the pulpit and saying to the man or women who is hearing the sermon or reading the book "Now, listen, this is what I suggest you should do differently". Its the "so what?" question. In business for example, people can give you vast amounts of data but without conclusions, application, things we should do differently, its all very interesting but without application its academically interesting only. The same in Christian teaching.
So what sparked Ryle to write "Holiness"? In his day, the Keswick Movement was going strong. Keswick (its an annual Christian conference in the town of Keswick in the English Lake District) as an event today is excellent, but the C19th theology coming out of Keswick was dangerous. Its watchword was "let go and let God". Like all heresies, there is much of truth in this. We can do nothing by ourselves, we don't earn our way to God, faith is his free gift. But as Ryle points out "is it wise to think of faith as the one thing needful...that the holiness of (Christians)...is by faith only and not at all by personal exertion?"("No" is the answer, in case you were wondering). This deviation comes from a confusion between two core theological concepts - faith and sanctification. In guarding jealously and rightly the "faith alone" of the Reformers it is very easy to swerve as it were from one side of the road to the other - avoid the crash barrier and drive into the tree - by failing to distinguish between faith ( a perfect, one time event in which we have no active role) and sanctification (an imperfect, continuous event in which we emphatically do have a role.) We seem to have thrown out the baby of sanctification with the bathwater of legalism. This is a common thought of people of other faiths. They think that the Christian view is something like "I am saved so I can do what I wish." As Voltaire said "God will forgive, that's his business". This book is the perfect antidote to that fatal error.
Ryle points out how much the bible has to say about being holy - or maybe better put the Christian is commanded in many places to become like the Lord Jesus. When our friends and family who are not Christians point out the many things in our life which are wrong - hypocrisy basically because we say one thing and do something else - then the answer is to admit our faults and become holy. As Ryle points out - "Be holy for I am holy" (1 Peter 1:15) and "Without holiness no one can see the Lord". Holiness is important, argue Ryle, also because its the way we do good to others. The description "do gooder" very sadly has a negative connotation in English but its a biblical injunction. Ryle says "It makes (the Christian faith) beautiful and draws men to consider it, like a lighthouse seen afar off". If we dont have that gravitational pull, if we dont see people coming to the "lighthouse" then it may well be because we dont have the "light" - the holiness.
Ryle then moves on to answer the next question, again a rather obvious one "If we need holiness, how do we get it"?. What are the practical means available? He also sprinkles the book with warnings to the Christian. Lot's wife, for example, whom as you may or may not recall was very reluctant to leave Sodom when it was being destroyed by God. She was being pulled out by the angels but lingered and as she fled was turned into a pillar of salt.She wanted to escape the coming judgement but she felt the powerful gravitational pull of this life and money and possessions and the cares of this world. As Ryle points out, she is a solemn warning to all Christians of the danger of "wanting to have our cake and eat it too". Or as Ryle says "They (people like Lot's wife) are neither one thing or another: not quite a thorough going Christian and not quite men of the world". But Ryle doesn't leave us there - he brings us to a much more encouraging example - the thief on the cross.
So in summary, if you feel comfortable and relaxed in your faith, if you feel all is good with your Christian life, if you feel you are really a very decent sort of chap or chapess, then dont read Ryle. for he will shake you awake, pour cold water on you, slap you round the face and generally prod you into life. Let me give the man himself the last word. This is typical of Ryle "Believers in the Lord Jesus of every church...I feel much for you. I know your course is hard. I know it is a sore battle you have to fight. I know you are often tempted to say "It is of no use" and to lay down your arms altogether. Cheer up, dear brothers and sister. take comfort, I entreat you...Be encouraged to fight on. the time is short. the Lord is at hand. The night is far spent. Millions as weak as you have fought the same fight. Not one of all these millions has finally been led captive by Satan. Mighty are your enemies - but the Captain of your salvation is mightier still...Cheer up. Be not cast down. What though if you lose a battle or two? You shall not be cast down. You shall not be destroyed. Watch against sin and sin shall not have dominion against you. Resist the devil and he shall flee from you...You shall find yourselves in the end more than conquerors - you shall overcome."
So for advice on how to "overcome", read Ryle