When I looked, behold a hand was put forth by a spirit unto me, and a roll of a book was therein which he unrolled in my sight; it was written on the front and on the back (2:9, 10).

And in John: 

     I saw upon the right hand of Him that sat on the throne a
     book written within and on the back, sealed up with seven
     seals (Apoc. 5:1).

259.  The existence of writings in the heavens is a provision of the Lord for the sake of the Word; for the Word in its essence is Divine truth, and from it is all heavenly wisdom, both with men and with angels; for the Word was dictated by the Lord, and what is dictated by the Lord passes through all the heavens in order and terminates with man.  Thereby it is adapted both to the wisdom of angels and the intelligence of men.  Thereby, too, the angels have a Word, and read it the same as men do on the earth, and also draw from it their doctrinals, and preach from it (n. 221).  It is the same Word; but its natural sense, which is the sense of the letter with us, does not exist in heaven, but only the spiritual sense, which is its internal sense.  What this sense is can be seen in the small treatise on The White Horse spoken of in the Apocalypse.

260.  A little paper was at one time sent to me from heaven, on which there were a few words only written in Hebrew letters, and I was told that every letter involved arcana of wisdom, and that these arcana were contained in the inflections and curvatures of the letters, and thus also in the sounds.  This made clear to me what is signified by these words of the Lord: 

     Verily I say unto you, until heaven and earth pass away,
     one iota or one tittle shall not pass away from the law
     (Matt. 5:18).

That the Word in every tittle of it is Divine is known in the church; but just where the Divine lies hid in every tittle has not been known heretofore, and therefore shall be told.  In the inmost heaven the writing consists of various inflected and circumflected forms, and the inflections and circumflections are in accordance with the forms of heaven.  By means of these angels express the arcana of their wisdom, and also many things that they are unable to express in spoken words; and what is wonderful, the angels know this writing without training or a teacher, it being implanted in them like their speech (see n. 236); therefore this writing is heavenly writing.  It is implanted because all extension of thoughts and affections and consequent communication of intelligence and wisdom of the angels proceeds in accordance with the form of heaven (n. 201); and for the same reason their writing flows into that form.  I have been told that the most ancient people on this earth, before letters were invented, had such writing; and that it was transferred into the letters of the Hebrew language, and these letters in ancient times were all inflected, and none of them, as at present, were bounded by straight lines.  Thus it is that in the Word Divine things and arcana of heaven are contained even in its iotas, points and tittles.