There is not a lot written or known about him in the english speaking world, but I hope there will be soon. Pope Benedict made him a Doctor for a reason, so we should use this grace to help us in our spiritual life. He really is a wonderful spiritual director. This is what Pope Benedict said about him in his Apostolic Letter proclaiming him a Doctor of the Church
The declaration that a saint is a Doctor of the Universal Church implies the recognition of a charism of wisdom bestowed by the Holy Spirit for the good of the Church and evidenced by the beneficial influence of his or her teaching among the People of God. All this was clearly evident in the person and work of Saint John of Avila. He was often sought out by his contemporaries as a master of theology, gifted with the discernment of spirits, and a director of souls. His help and guidance were sought by great saints and acknowledged sinners, the wise and the unlearned, the poor and the rich; he was also responsible for important conversions and sought constantly to improve the life of faith and the understanding of the Christian message of those who flocked to him, eager to hear his teaching. Learned bishops and religious also sought him out as a counsellor, preacher and theologian. He exerted considerable influence on those who came into contact with him and on the environments in which he moved.
The thing that I got most out of his letters was learning to embrace suffering out of love of God, learning to trust and love God during the hard times no matter what, and keeping the Cross before all things. He truly is a wonderful spiritual director. These are some excerpts from his letters on suffering:
To a widow:
Let none deceive themselves. but let them feel assured that, as the King of Heaven entered his kingdom through tribulations, we must reach it by the same point. There is but one way - "Christ and Christ crucified''. If we seek a different road, we shall not find it. We should lose ourselves by any other path, and find that, however hard the sufferings in this world may be, those in the next world are far worse.... Although your life may not be a very happy one, it will greatly profit your soul, for by it you will purge away your sins, you will imitate Christ on the cross, and you will hold the certain hope of gaining his eternal kingdom.To an invalid:
Ever keep the Cross before your eyes, and unite your heart to him who placed himself upon it. Do not be satisfied until suffering becomes sweet for you, for that is the sign of true love... The Almighty does not wish you to feel lonely and sorrowful out of any ill will He bears you, but because His blessed Son was afflicted, and God would not have us unlike Him. Nothing pleases Him so well as to see in us a resemblance to His Only -Begotten Son. What so touches the soul as to see the Lord upon the Cross tortured for the love of us? The more afflicted and deformed by pain he appears, the more beautiful he seems to us; so the more we suffer for Him, the better will his Father look to love on us. Thus, we strive to beautify our souls with the crimson hue of suffering to win God's favor, just as fashionable women suffer pain and take trouble to attract the admiration of men.
To friends under threats and persecution:
God forbid that our souls should find rest in or choose any other lot but that of suffering beneath our Lord's Cross. I know not if bearing the cross can be called ''pain'' , for to my mind it is to repose on a bed of down and roses.To a grieving mother:
It is no easy matter to be the friend of Jesus Christ. Suffering born for Him is the only sure way to test which is the true and which is the false friend... Learn to love God as he loves you, and know that a true love will make you give yourself wholly to him, and keep back nothing for yourself. Do not fear to place yourself in God's hands, abandoning yourself entirely to him, for all that He holds is safe, and all else will certainly be lost.To a friend:
Forgetting all things, let us go to God, and abide entirely in Him; let us fast from all consolation in any creature, so that, as our souls dwell in solitude. God may come fill them, because they are empty of all else. When you place yourself in God's presence, endeavor rather to listen to Him than to speak with Him, and strive more to love Him and then learn from Him.To a young woman:
Close your eyes to all that afrights you and trust in the wounds of Christ, who received them for your sake, and you will find rest.To a student:
Brace up your heart to suffer afflictions, for without the battle there is no victory, and the crown is only for the conqueror. Think not that your burden is heavy; it is very light, compared with what you deserve to have to bear and with what Jesus Christ our Lord bore for your sake; it is slight indeed in comparison with the reward it will bring you. Remember that we shall soon quit this world, and then all the past will seem to us like a short dream. and we shall see that it is better to have labored than to have rested here. Learn how to profit by your sorrows, for they bring great riches to the soul. They cleanse it from past sin; what fire is to gold, that tribulation is to the just man, whose heart it purifies... Soon the vanity of this world will be unmasked, and the Kingdom of God will be revealed. Live here as a stranger - your body on earth, but your heart above - so that when our Lord calls you, he may not find you sleeping, but ready to go with Him, and to hear the sweet words "'well done, thou good and faithful servant, enter thou into the joy of thy Lord''.St John of Avila - pray for us that we may learn to embrace suffering so that we can embrace Jesus in Heaven.