Thanks to German Diction, here is Dietrich Fischer-Dieskau singing this piece (with perfect consonants and puckered vowels): http://www.youtube.com/watch?v=ZDFo_2SL0a8
Schubert's piece consists of six strophes, set poetically
aabb ccdd eeff...
a b a' b' a'' b''.
In this poem, the author reminisces about a tree where he has grown up, and finds himself needing to journey away from that spot, but misses it still. The phrase structure of each a b group is:
( a )( a ) ( b )( b' )
2 PACs HC PAC
where a consists of two identical phrases, and b has two phrases which start the same but end differently. (Schubert, preferring to keep his listeners interested, did not stick with this exact framework for every strophe, but this is generally true.)
The first two strophes are in a very stable E major, and work to set the stage. "So, there's this tree..." Unlike the very mobile intro, the accompaniment for the opening two stanzas is very block-chordal, making space for the singer to tell the story. Then as we move to stanza 3, ('Ich musst auch heute wandern') the same a melody is sent but now in E minor, allowing for all that lovely text-painty mixture chord stuff to happen. This seems to reflect the singer's reluctance to leave this place of such happiness and memories. We return to E major for stanza 4, with that same b melody with a slightly more embellished piano part, while the singer speaks as the tree, fondly calling him back to that peaceful spot.
In stanza 5 things get weird - we tonicize bVI (C natural) and maintain a minor mode feeling for all of this stanza. This is appropriate, since the singer is recalling a time when he walked past it in the dark and a cold wind blew, removing his hat, which he left behind. It is strange that Schubert sets the tree parts so warmly, and the singer, determined to avoid his special peaceful spot, must acheive his goal with a bunch of strange, unsettled-feeling harmonies. At this point the book authors want me to mention that this tonicization of b6 (Le) was foreshadowed in the intro, with the "La-sol" motive in measures 2, 20 and 24.
In the final stanza, the singer goes back to reminiscing, in warm E major, with triple-y but still simple accompaniment. This only serves to drive home how much he really wishes to say, especially when Schubert prolonged the phrase in measures 73-76 by repeating "you would have found peace". This is clearly the longing of the singer to stay by his special tree. Why must he go? Because the song cycle is titled "Winter Journey". So we can't stay in the same place (or warm) for long.
Interesting fact: "Linden tree" is actually what my middle name, Lindsey, is supposed to mean